Doped Layer Research Articles

High-Entropy Layered Oxide Cathode Materials with Moderated Interlayer Spacing and Enhanced Kinetics for Sodium-Ion Batteries.

Sodium-ion batteries (SIBs) with low cost and environmentally friendly features have recently attracted significant attention for renewable energy storage. Sodium layer oxides stand out as a type of promising cathode material for SIBs owing to their high capacity, good rate performance, and high compatibility for manufacturing. However, the poor cycling stability of layer oxide cathodes due to structure distortion greatly impacts their practical applications. Herein, a high entropy doped Cu, Fe, and Mn-based layered oxide (HE-CFMO), Na0.95Li0.05Mg0.05Cu0.20Fe0.22Mn0.35Ti0.13O2 for high-performance SIBs, is designed. The HE-CFMO cathode possesses high-entropy transition metal (TM) layers with a homogeneous stress distribution, providing a moderated interlayer spacing to maintain the structure stability and enhance Na+ ion diffusion. In addition, Li doping in TM layers increases the Mn valence state, which effectively suppresses John-Teller effect, thus stabilizing the layered structure during cycling. Furthermore, the use of nontoxic and low-cost raw materials benefits future commercialization and reduces the risk of environmental pollution. As a result, the HE-CFMO cathode exhibits a super cycling performance with a 95% capacity retention after 300 cycles. This work provides a promising strategy to improve the structure stability and reaction kinetics of cathode materials for SIBs.

Charge Transfer Plasmonics in Bespoke Graphene/α-RuCl3 Cavities.

Surface plasmon polaritons (SPPs) provide a window into the nano-optical, electrodynamic response of their host material and its dielectric environment. Graphene/α-RuCl3 serves as an ideal model system for imaging SPPs since the large work function difference between these two layers facilitates charge transfer that hole dopes graphene with n ∼ 1013 cm-2 free carriers. In this work, we study the emergent THz response of graphene/α-RuCl3 heterostructures using our home-built cryogenic scanning near-field optical microscope. Using phase-resolved imaging, we clearly observe long wavelength, heavily damped THz SPPs in a series of variable-size graphene cavities. From this, we extract the plasmonic wavelength and scattering rate in the graphene/α-RuCl3 heterostructures. We determine that the measured plasmon wavelength and electronic scattering rate match our heterostructures' theoretically predicted values. Our results demonstrate that shaping graphene into bespoke cavity structures enables observation and quantification of SPPs in heavily doped graphene that are largely not addressable with other experimental techniques. Moreover, the manifest lack of metallicity observed in the adjacent doped α-RuCl3 layer provides significant constraints on the nature of the interfacial charge transfer in this 2D heterostructure.

Numerical optimization of inorganic p-Sb2Se3/n-ZrS2 heterojunction solar cells: achieving high efficiency through SCAPS-1D simulation

p-Sb2Se3 and n-ZrS2 materials show strong potential for cost-effective photovoltaic applications. This study presents a detailed numerical analysis of p-Sb2Se3/n-ZrS2 heterojunction solar cells using SCAPS-1D, focusing on how key parameters such as layer thickness, doping density, and bandgap have affected device performance. Critical photovoltaic metrics, such as built-in voltage (Vbi), carrier lifetime, depletion width (Wd), recombination rates, and photogenerated current, were examined. Our findings demonstrate that optimizing the p-Sb2Se3 absorber layer with a 1.0 eV bandgap, 5000 nm thickness, and doping density of 1020 cm−3 leads to a maximum efficiency of 32.14%, with a fill factor (FF) of 84.57%, short-circuit current density (Jsc) of 47.61 mA cm−2, and open-circuit voltage (Voc) of 0.792 V. For the ZrS2 buffer layer, the best performance was achieved with a 1.2 eV bandgap, 200 nm thickness, and doping density below 1 × 1020 cm−3. These optimized parameters significantly enhanced carrier separation and minimized recombination losses, leading to improved power conversion efficiency. In addition to theoretical optimization, this study emphasizes the practical potential of these materials for real-world applications. The combination of Sb2Se3 and ZrS2 offers a low-cost fabrication process suitable for scalable commercial solar cell production while maintaining high efficiency. These results underscore the viability of p-Sb2Se3/n-ZrS2 heterojunctions as promising candidates for next-generation clean energy solutions.

Lead-free Cs2TiBr6 perovskite solar cells achieving high power conversion efficiency through device simulation

Recently, lead-based perovskite solar cells (PSCs) have gained significant attention in the photovoltaic industry due to their remarkable properties such as high bandgap and high absorption coefficient. However, challenges such as toxicity, instability, and short shelf life limit the use of inorganic-organic lead-based PSCs. To address these issues, researchers introduced eco-friendly, lead-free, and stable cesium titanium (Cs2TiBr6) single-halide absorber material. The aim of this work is to perform the numerical modelling and simulation of FTO/SnO2/Cs2TiBr6/CBTS/Au structure incorporating interfacial defect layers (IDL) using SCAPS-1D to examine and study its characteristics properties about various photovoltaic (PV) parameters such as light-absorbing layer thickness, charge transport layer thickness, doping, defect density, operating temperature, and quantum efficiency (QE). After evaluating these parameters, the proposed single-halide Cs2TiBr6-based structure shows superior performance as compared to previously reported experimental and simulation-based Cs2TiBr6 perovskite structures. The results show a maximum power conversion efficiency (PCE) of 24.24 %, with a fill factor (FF) of 88.9 %, an open-circuit voltage (VOC) of 1.31 V, and a short-circuit current density (JSC) of 20.76 mA/cm2. This work encourages researchers to develop low-toxic, and stable PSCs for the future solar cell industry.

Transition Metal Dichalcogenides in Electrocatalytic Water Splitting

Two-dimensional transition metal dichalcogenides (TMDs), also known as MX2, have attracted considerable attention due to their structure analogous to graphene and unique properties. With superior electronic characteristics, tunable bandgaps, and an ultra-thin two-dimensional structure, they are positioned as significant contenders in advancing electrocatalytic technologies. This article provides a comprehensive review of the research progress of two-dimensional TMDs in the field of electrocatalytic water splitting. Based on their fundamental properties and the principles of electrocatalysis, strategies to enhance their electrocatalytic performance through layer control, doping, and interface engineering are discussed in detail. Specifically, this review delves into the basic structure, properties, reaction mechanisms, and measures to improve the catalytic performance of TMDs in electrocatalytic water splitting, including the creation of more active sites, doping, phase engineering, and the construction of heterojunctions. Research in these areas can provide a deeper understanding and guidance for the application of TMDs in the field of electrocatalytic water splitting, thereby promoting the development of related technologies and contributing to the solution of energy and environmental problems. TMDs hold great potential in electrocatalytic water splitting, and future research needs to further explore their catalytic mechanisms, develop new TMD materials, and optimize the performance of catalysts to achieve more efficient and sustainable energy conversion. Additionally, it is crucial to investigate the stability and durability of TMD catalysts during long-term reactions and to develop strategies to improve their longevity. Interdisciplinary cooperation will also bring new opportunities for TMD research, integrating the advantages of different fields to achieve the transition from basic research to practical application.

Optimization and characterization of doped photoactive layer P3HT: ICBA for organic optoelectronic applications

A doped bulk heterojunction P3HT: ICBA active layer was studied, aiming at the effects of chromium chloride (CrCl2) and Cobalt chloride (CoCl2) doping. The study involved linear optical and electrical characterization to analyze the impact of these additives on the photoactive layer's performance. The electrical properties of doped P3HT: ICBA revealed enhancements with CrCl2(5%wt), CrCl2(10%wt), CoCl2(5%wt), and CoCl2(5%wt) (5%wt) by 8.5x, 11x, 10x, and 14x respectively, compared to pure P3HT:ICBA under dark/light conditions. This improvement is attributed to enhanced internal charge generation. The study also examined the effect of thermal treatment on the active layer from 20 ºC to 65 ºC under dark/light conditions. Additionally, the doped photoactive layer samples were tested as optical sensors under white, green, and red light, with a slightly higher optical response under white light. The findings confirm that doping P3HT: ICBA with CoCl2 and CrCl2 improves optical and electrical responses due to better charge transfer and generation.

Synergistic enhancement of lithium iron phosphate electrochemical performance by organic zinc source doping and crystalline carbon layer capping

In this study, lithium iron phosphate (LFP) is prepared as cathode material by hydrothermal synthesis method and the combined effect of doping and capping is applied to co-modify it. We thoroughly investigate how Zn2+ doping and PA capping layer affect the crystal structure, microscopic morphology, and electrochemical properties of LFP cathode materials. The experimental results show that when co-modified with 5 % Zn2+ doping combined with 7 % PA capping layer, the resulting cathode material exhibits a discharge specific capacity of 165.5 mAh g−1, and the capacity retention rate can still be maintained at a high level of 98.6 % after 200 charge–discharge cycles.

Complex Diagnostics of Silicon-on-Insulator Layers after Ion Implantation and Annealing

A technology was developed for activating ion-implanted dopants in silicon-on-insulator layers at a low annealing temperature (600°C) using the pre-amorphization technique of a silicon device layer. In the case of phosphorus implantation, silicon was amorphized directly by dopant ions. In the case of boron implantation for pre-amorphization, the layers were preliminary irradiated with argon or fluorine ions. Complex diagnostics of the implanted layers was carried out using secondary ion mass spectrometry, X-ray diffractometry and small-angle X-ray reflectometry. The combination of methods made it possible to characterize the impurity distribution, the degree of silicon crystallinity, the layer thicknesses, and the interface widths in structures. The results of diagnostics of the structure and composition correlate well with calculations in the SRIM software package and the electrophysical characteristics of the layers after annealing. It was shown that the use of argon for pre-amorphization of silicon interfered with the recrystallization process and did not make it possible to achieve acceptable electrical characteristics of the doped layer. Amorphization with phosphorus and pre-amorphization with fluorine during boron implantation allowed obtaining the required values of the resistance of the doped layers after annealing at a temperature of 600°C. The use of a complex approach made it possible to optimize the modes of amorphization, ion doping, and annealing of silicon-on-insulator structures at low temperatures, necessary for the creation of light-emitting device structures based on silicon-germanium nanoislands.

Assessment of photovoltaic efficacy in antimony-based cesium halide perovskite utilizing transition metal chalcogenide

Antimony-based perovskites have been recognized for their distinctive optoelectronic attributes, standard fabrication methodologies, reduced toxicity, and enhanced stability. The objective of this study is to systematically investigate and enhance the performance of all-inorganic solar cell architectures by integrating Cs3Sb2I9, a perovskite-analogous material, with WS2—a promising transition metal dichalcogenide—used as the electron transport layer (ETL), and Cu2O serving as the hole transport layer (HTL). This comprehensive assessment extends beyond the mere characterization of material attributes such as layer thickness, doping levels, and defect densities, to include a thorough investigation of interfacial defect effects within the structure. Optimal efficiency was observed when the Cs3Sb2I9 absorber layer thickness was maintained within the 600-700 nm range. The defect tolerance for the absorber layer was identified at 1×1015/cm3, with the ETL and HTL layers exhibiting significant defect tolerance at 1×1016/cm3 and 1×1017/cm3, respectively. Furthermore, this study calculated the minority carrier lifetime and diffusion length, establishing a strong correlation with defect density; a minority carrier lifetime of approximately 1 µs was noted for a defect density of1×1014/cm3 in the absorber layer. A noteworthy finding pertains to the balance between the high work function of the back contact and the incorporation of p-type back surface field layers, revealing that interposing a highly doped p+ layer between the Cu2O and the metal back contact can elevate the efficiency to 21.60%. This approach also provides the freedom to select metals with lower work functions, offering a cost-effective advantage for commercial-scale applications.

Enhanced CZTSSe Thin‐Film Solar Cell Efficiency: Key Parameter Analysis

This work presents a numerical simulation study on CZTSSe‐based thin‐film solar cells using Silvaco Atlas software, focusing on optimization and loss analysis. Starting from an initial power conversion efficiency of 12.73%, the ZnO/CdS/CZTSSe cell structure is systematically optimized. Through precise adjustment of layer thickness and doping density, the efficiency is improved to 18.75%. The optimal parameters are 2.5 μm (1017 cm−3) for CZTSSe, 0.01 μm (1018 cm−3) for CdS, and 0.02 μm (1019 cm−3) for ZnO. Loss analysis reveals that increasing CZTSSe thickness beyond 2.5 μm leads to higher bulk series resistance, while thicker CdS and ZnO layers reduce photocurrent generation. Doping density significantly impacts open‐circuit voltage, while layer thickness primarily affects short‐circuit current and fill factor. Performance improves at lower temperatures, achieving 22.2% efficiency at 250 K. These findings provide valuable insights for developing high‐efficiency CZTSSe solar cells.

High-Volume SiC Epitaxial Layer Manufacturing-Maintaining High Materials Quality of Lab Results in Production

Typically, research and development (R&D) results of epitaxial layer growth show superior properties of the grown layers compared to high volume results. Layer uniformities are excellent and achieved defect densities are low compared to typical results. In particular, the conversion of basal plane dislocations (BPD) from the silicon carbide (SiC) substrate is in focus to reduce bipolar degradation of p-n-junctions. It is a great challenge to maintain those excellent results in high-volume manufacturing considering all the factors that impact the properties of the epilayer. Thus, quality of the layers, high throughput and low cost have to be assessed to find a compromise between these key factors. In this paper we present results on the growth of epitaxial layers on 150 mm and 200 mm 4° off-oriented 4H-SiC substrates using warm-wall multi-wafer chemical vapor deposition (CVD) systems. Single wafer data of the key epitaxial layer parameters, thickness, doping and defect densities, are compared to batch and lot results, as well as to statistical data of several hundreds of wafers produced. Improvements in wafer-to-wafer (w-t-w) doping uniformity could be achieved for instance by implementation of an on-wafer temperature measurement. Substrate impact on defect levels is shown comparing X-ray topography (XRT) results of bare substrate wafers and defect analysis of epilayers on sister wafers from the same crystal. Statistical defect data and resulting predicted yield loss also show a dependence on substrate suppliers. For the first time we show w-t-w and run-to-run (r-t-r) results of doping and thickness measurements on 200 mm substrates. Also, defect results of epilayers on 200 mm wafers are compared to results on 150 mm.

Investigating the effect of Y3+/La3+ co-dopant on Ba site of BaSnO3 as an efficient photoanode for dye sensitized solar cell application

This study aims to improve the performance of barium stannate (PBS) based photoanode by co-doping with rare earth elements (Y3+ and La3+) and optimizing charge transport in the mesoporous TiO2 (meso-TiO2) as compact layer at the FTO interface. Employing Y3+ and La3+ dopant into BaSnO3 (YLB) at the FTO/meso-TiO2/YLB interface enhances light absorption and minimizes charge recombination. The resulting DSSC device, utilizing a meso-TiO2/YLB3 photoanode (PBS-3% of Y3+/La3+), achieves an efficiency of 3.79 %, with a high current density of 8.04 mA/cm2, a fill factor of 64.76 % and an open circuit voltage of 0.73 V. The synergistic effect of dopant and compact layer treatment purposefully improves photon and charge collection, enhancing overall device performance and reducing recombination at the interface. Consequently, the introduction of a compact layer-treated co-doped PBS photoanode emerges as a promising alternative for a charge transport layer in DSSC.

Quantum landau levels in n-type modulation-doped GaAs/AlGaAs coupled double quantum wells

The electron properties of two coupled quantum wells with a δ doping layer are investigated by solving simultaneous Schrödinger and Poisson equations while subjecting the nanosystem to a magnetic field ranging from 0 T to 30 T. The calculation is conducted using the FEniCS Project and Python programming within the effective mass and Hartree approximations. The presence of a magnetic field significantly modifies the electron density, a factor not previously considered, making this the first work to address the modification of the density of states of an electron system by a magnetic field and showing the formation of Landau levels in quantum wells. We demonstrate that the magnetic field significantly alters the electron density, Landau levels, and Fermi energy. Furthermore, these physical parameters are influenced by the dimensions of the nanostructure, represented by Ld and Lb, as well as the properties of the layers, such as δ, nd, and xi.

Using Atomic Layer Deposition to Create Mixed Metal Oxide Electrodes for H2O2 Generation through Water Oxidation

The electrochemical synthesis of H2O2 through water oxidation provides a means of producing a useful chemical and potential fuel without the input of fossil fuels. Highly stable metal oxides like TiO2 and SnO2 surfaces have shown activity as electrocatalysts for oxidative H2O2 generation, but often require high overpotentials that result in parasitic side reactions. Using atomic layer deposition (ALD) to introduce well-distributed layers of MnOx dopant one can lower the required overpotential of TiO2 and SnO2 surfaces for H2O2 production. Even a single sub-surface layer of MnOx can alter the redox behavior of a 5 nm thick oxide film. While the doped films maintained reversible Mn redox peaks and prevent the total dissolution of the deposited Mn, in-situ inductively coupled mass spectrometry did reveal loss of Mn from the film at applied potentials close to the expected onset potential of the 2e- water oxidation reaction. The depth of sub-surface MnOx was varied to determine the effect on both electrode activity, selectivity, and stability. In addition, the use of either inert and oxidizing annealing atmospheres was used to control both the distribution and the charge-state of the Mn species. This work provides some indication of how manganese-doped metal oxide electrodes degrade during operation and how controlling the surface can improve the activity and stability of the device. This study may also provide a framework of how other redox active species can be embedded within more stable oxide matrices using ALD methods to maximize stability and activity.

Doping of Porous Transport Layers to Optimize Electrical Contact Behaviour in PEM Water Electrolysis Cells

A high overall efficiency is crucial for large-scale polymer electrolyte membrane water electrolysers. Due to the harsh environment at the anode, a titanium oxide layer with high electrical resistivity passivates porous transport layers (PTL). A common used way to overcome this problem is noble metal coating (e.g. with platinum, gold or iridium). [1] For the very first time, we present a new and inexpensive way of maintaining the high conductivity of PTLs by doping the titanium surface that faces the catalyst layer. Sun et al. [2] modelled the conductivity of doped titanium oxide for different elements. With respect to their results and Koech et al. [3] we chose tin, niobium, antimony and yttrium as dopants. The implantation was carried out at the Ion Beam Center of the HZDR in Dresden, Germany. All doped PTLs displayed a lower cell voltage than the undoped reference as visible in figure 1a). While tin improves in the range of 2-3 % at a current density of 2A/cm², the other dopants best results reach values of over 4 % with niobium achieving the best performance with 4.4 % improvement (see figure 1b) for comparison). Figure 1c) shows the high frequency resistance (HFR) originating from impedance measurements. The observable improvement of up to 11.4% at 2A/cm² proves the fact that the advantage corresponds to a better contact resistance due to a lower resistance of the doped titanium oxide layer. The improvement in percent presents figure 1d).The measurement results show that doping can have a great impact on the contact resistance of titanium PTLs. These results open a new opportunity in the manipulation of porous transport layers for enhanced contact behaviour, where no experimental publications exist yet. Especially in comparison to noble metal coatings like iridium, doping has an enormous cost advantage when using non noble metals with the potential of lowering the overall electrolyser system costs while increasing its efficiency.[1] Liu, C., Shviro, M., Gago, A. S., Zaccarine, S. F., Bender, G., Gazdzicki, P., Morawietz, T., Biswas, I., Rasinski, M., Everwand, A., Schierholz, R., Pfeilsticker, J., Müller, M., Lopes, P. P., Eichel, R.-A., Pivovar, B., Pylypenko, S., Friedrich, K. A., Lehnert, W., Carmo, M., Exploring the Interface of Skin-Layered Titanium Fibers for Electrochemical Water Splitting. Adv. Energy Mater. 2021, 11, 2002926. https://doi.org/10.1002/aenm.202002926[2] Hu Sun, Zhu-tian Xu, Di Zhang. First-principles calculations to investigate doping effects on electrical conductivity and interfacial contact resistance of TiO2, Applied Surface Science, Volume 614, 2023, 156202, ISSN 0169-4332, https://doi.org/10.1016/j.apsusc.2022.156202.[3] Koech, R.K.; Ichwani, R.; Oyewole, D.; Kigozi, M.; Amune, D.; Sanni, D.M.; Adeniji, S.; Oyewole, K.; Bello, A.; Ntsoenzok, E.; et al. Tin Oxide Modified Titanium Dioxide as Electron Transport Layer in Formamidinium-Rich Perovskite Solar Cells. Energies 2021, 14, 7870. https://doi.org/10.3390/en14237870 Figure 1

Modifying Polymer-Based Hard Carbons for Enhanced Understanding of Sodium Storage Properties

Numerous theories on the storage of sodium in hard carbons can be found in the literature. In particular, understanding the contributions of (heteroatom) doping, porosity and graphitic layers is of great importance. Much of the current literature on hard carbons uses different biomaterials as precursors in order to improve the sustainability of the synthesis. However, large differences in the composition of the starting materials and the presence of foreign atoms make a systematic investigation of the storage process extremely difficult.Therefore, a hard carbon material based on furan resins was used in this work to obtain a well-defined starting material that can be modified systematically. This allows a detailed investigation of the effects caused by those modifications. Modifications can be achieved by directly adding various template materials to the polymerization process. Both doping with heteroatoms by adding template chemicals such as boric acid and the introduction of graphitic layers by adding high-purity graphite during polymerization were investigated.Addition of boron and phosphorus heteroatoms led to an increase in reversible capacity up to 240 mAh g-1 from 150 mAh g-1 for carbonization temperatures as low as 650°C. Formation of a potential plateau was observed for boron doping, which is usually found at higher carbonization temperature surpassing 1000°C. Utilizing Raman and XRD spectroscopy, crystallite size was found to be decreasing with phosphorus doping, while boron doping led to an increase. This increase could be a possible explanation for the observed capacity plateau.The addition of high-purity carbon samples, such as KS6L graphite or graphene, allowed for a targeted introduction of single- and multi-layer graphitic domains without alteration of additional properties. Increasing graphite content up to 5 wt-% during polymerization resulted in enhanced electrochemical characteristics, including increased sodium intercalation into the lattice and shift of the sloping proportion to lower potentials. Further increase up to 10 wt-% led to a vanishing of the plateau potential and a lowering of the reversible capacity. The results indicate that the interlayer spacings has now decreased below a threshold, which prohibits the sodium from intercalation between the graphitic layers. Additionally, doping Hard Carbons with graphene revealed a capacity decrease at content ratios as low as 2 wt-%, emphasizing the significance of both the stacking and interlayer spacing of the graphitic lattice, as well as the chemical composition, for efficient sodium storage.In summary the results presented provide an enhanced understanding into the sodium storage properties of Hard Carbons, which help improve the design of synthesis processes for more cost-efficient and high-performance carbon materials. Figure 1

(Invited) Consideration on Gate Stack Formation Processes of Ultrawide Bandgap Ga2O3 with SiO2 Dielectric Layer

MOSFETs on β-Ga2O3 are expected to be a high-efficient and cost-effective alternative option of high-voltage power devices. Taking account of the reliability and the large conduction-band offset against β-Ga2O3, it would be reasonable to employ SiO2 as the gate dieletric. In this study we investigated the effects of post-deposition annealing (PDA) on SiO2/β-Ga2O3 MOS gate stacks, in terms of the MOS electrical characteristics and the band alignment.β-Ga2O3 (001) wafers with ~2×1016 cm-3 n-type doped epitaxial layers were cleaned in diluted HF solution, and SiO2 films were deposited by electron-beam (EB) evaporation of Si in O2 ambient of ~1×10-2 Pa, followed by PDA at various temperatures from 600 to 1000℃ in either O2 or N2 ambient. Au was evaporated as gate electrode to form MOS capacitors. X-ray photoelectron spectroscopy (XPS) was conducted on the stacks with ~3nm-thick SiO2 for the evaluation of band alignment. Ultraviolet photoelectron spectroscopy (UPS) was also employed to determine the band diagram of β-Ga2O3 (001).Nearly-ideal capacitance-voltage characteristics were obtained for the MOS capacitor fabricated with O2-PDA at 1000℃. The interface state density (Dit) determined by conductance method decreased down to ~1010 cm-3 at the energy level of EC−0.2 eV by PDA at higher temperature. The hysteresis width (ΔVhys) of C-V curves was smaller for the samples annealed at higher temperatures. The flatband voltage (VFB) shift after O2-PDA resulted in VFB close to the ideal value estimated from the physical properties of Au and Ga2O3, suggesting that fixed charge density at the interface would be minimized. However, PDA in N2 at 1000℃ resulted in a negative shift of VFB, which indicates the formation of positive fixed charges in the stack. The beneficial influences of O2-PDA on those characteristics suggest that an oxygen deficiency introduced near the interface is one of the origins of interface defect states. It is noteworthy that Ga3d XPS on the surface of Ga2O3 substrate always shows a tailing in lower binding energy side, which is indicating oxygen deficiency on the surface. The intensity of this lower-binding-energy component reduced significantly when a bare-Ga2O3 substate was annealed in O2, however, it did not decrease efficiently even after O2-PDA when the surface was covered with SiO2. This is probably due to the oxygen rearrangement at SiO2/Ga2O3 interface determined by the difference of material properties of those oxides. This fact suggests that the Ga2O3 surface easily forms oxygen vacancies when it is covered with SiO2. This would be the reason why the formation of interface defect states is not suppressed without O2-PDA.Next the band diagram of β-Ga2O3 (001) substrate was investigated by UPS analysis where the energy level of valence band edge referring to the vacuum level was evaluted from the energy difference between minimum (cut-off) and maximum edges of the obtained kinetic energy spectra of photoelectrons. As a result we found the valence band edge of of β-Ga2O3 (001) was ~8.2 eV below the vacuum level, where the influences of O2 annealing at 1000℃ on the valence band edge energy level was limited to the shift within ~0.1eV. This would tell us the valence band offset between SiO2 and Ga2O3 should be around ~1.1eV, and the conduction band offset between them is to be around 2.8-2.9eV, by taking account of the well-reported SiO2 band diagram and assuming the bandgap of β-Ga2O3 as 4.7eV. On the other hand, the valence band offset estimated from the deconvolution of the XPS valence band spectrum for a ~3nm-thick SiO2/β-Ga2O3 stack from the energy edge difference between the deconvoluted spectra corresponding to SiO2 and Ga2O3, was a few hundreds of mV smaller than the above expected value (~1.1eV). This discrepancy is indicating the formation of an interface dipole layer between SiO2 and Ga2O3 with a pair of nagative and positive charges aligned at the interface to cause a shift in the band alignment. The magnitude of such dipole was indicated to be more significant (~0.5eV) for the stack after PDA at 1000℃, whereas it was less (0.2~0.3eV) after PDA at 600℃.In conclusion, we demonstrated that SiO2/β-Ga2O3 (001) MOS capacitors showed nearly-ideal electrical characteristics with significantly reduced interface defect density and small fixed charge density by applying O2-PDA. The band alignment of SiO2/β-Ga2O3 (001) MOS stack was clarified by photoelectron spectroscopy to confirm a very large conduction band offset of the stack, but an influence of the formation of interface dipole layer between SiO2 and Ga2O3 on the band alighment was also indicated.

Breakdown up to 12 Kv in NiO/β-Ga2O3 Vertical Heterojunction Rectifiers

Vertical heterojunction NiO/β n-Ga2O/n+ Ga2O3 rectifiers fabricated on 15 µm thick drift layers with carrier concentration 8.8 x1015 cm-3 and employing simple dual-layer PECVD SiNx/SiO2 edge termination demonstrate breakdown voltages (VB) up to 12 kV, on-voltage (VON) of ~2.2V and on-state resistance RON of 11.1-12 mΩ.cm2 . The breakdown field is ~8 MV. cm-1, close to the commonly accepted theoretical value. The associated power figure-of-merit, VB 2/RON is 13 GW·cm-2 . By sharp contrast, Schottky rectifiers concurrently fabricated on the same drift layers had maximum VB of 2.9 kV, but lower VON of 0.71-0.75 V. Transmission electron microscopy showed an absence of lattice damage between the PECVD and sputtered films within the device and the underlying epitaxial Ga2O3. The key advances are thicker, lower doped drift layers and optimization of edge termination design and deposition processes. Figure 1

(Invited) Preparation of N-Type and P-Type Doped Single Crystal Diamonds with Laser-Induced Doping and Microwave Plasma Chemical Vapor Deposition

In this study, n-type doped single crystal diamonds were successfully prepared under normal temperature and pressure conditions using laser-induced doping. 248nm pulsed laser beams with nanosecond duration were irradiated on the single crystal diamond substrate immersing in an 85% phosphoric acid solution and it introduced phosphorus doping to form an n-type doped thin layer. The resistivity of the doped region significantly decreased compared to that of the single crystal diamond. After depositing a titanium electrode, the resistivity of the doped film obtained by Van der Pauw Technique was determined to be 1.3×10-6 Ω·m. Raman spectroscopy confirmed the absence of carbon or graphite phases in the laser-induced doped diamond, indicating that the enhanced conductivity was due to phosphorus incorporation.Furthermore, p-type doped single crystal diamonds were successfully prepared by introducing boron during the growth process using Microwave Plasma Chemical Vapor Deposition（MPCVD）. It was demonstrated that the proposed technique can introduce impurities into single crystal diamonds to form doped conductive thin layers, which has potential applications in the field of microdevices and integrated circuits.

Pathfinding Process Development for the Realization of Atomic Precision Advanced Manufacturing (APAM)-Based Vertical Tunneling Field Effect Transistors for Enhanced Energy Efficiency

Since the end of Dennard scaling, where metal oxide semiconductor field effect transistor (MOSFET) operating frequency and energy efficiency improved with shrinking device dimensions [1], increasing transistor density is predicted to increase the total power consumption of a system [2]. A key limitation for MOSFETs is that the minimum rate of turn-on, or subthreshold swing (SS), is ~60 mV/decade at room temperature because of the Boltzmann statistics that dictate charge density. Thus, maintaining constant electric field without increasing energy consumption (i.e. gate bias) requires decreasing the SS by investigating alternative materials or device designs, like tunnel FETs (TFETs) [3]. Recent advances in atomic-scale control promise to provide control over quantum mechanical degrees of freedom which have hindered TFET performance in practice. These considerations make atomic precision advanced manufacturing (APAM) an appealing platform to realize a proof-of-concept TFET with atomic scale features [4,5].APAM can produce a 2D sheet of dopants in silicon beyond the solid solubility limit that can be patterned in-plane and capped with epitaxial silicon for strong carrier confinement in the out-of-plane direction (Figure 1). Indeed, improvements to planar TFETs that effectively have 1D channels with low on:off current ratios have been proposed by changing to a vertical geometry that leverages the carrier confinement afforded by 2D materials to create a 2D channel [6], though these materials are not typical in a silicon foundry. In contrast, APAM provides this carrier confinement while exclusively using materials and chemicals that are used in silicon foundries and with compatible processes [7]. In the APAM TFET (Figure 1.8.), a gate bias induces a layer of holes at the oxide/silicon interface that extends from the source, enabling tunneling between the 2D phosphorus-doped layer that comprise the drain and the 2D induced hole layer.As tunnelling occurs vertically through the epitaxial silicon cap, it becomes critical to determine the optimal growth temperature, to keep the dopants in a 2D sheet at low temperatures versus producing low-defect silicon at higher temperatures. Similarly, for optimal electric field control, it becomes critical to determine the optimal processing temperature to maintain the 2D dopant sheet and produce a low-defect gate oxide. The electronic thickness of the dopant layer can be measured using weak localization and the segregation of dopants out of the 2D sheet can be measured using secondary ion mass spectrometry. Our intial attemps at evaluating the electrical quality of the epitaxial silicon cap used PMOS transistors made with an ALD gate dielectric on APAM material without the buried phosphorus layer. Intuitively, we expect material grown at a higher temperature to produce a lower density of defects and therefore more performant PMOS, but find instead that the initial results demonstrate no systematic trend. These results potentially indicate there is an unknown variable obscuring the intentionally changed variable of growth temperature. Here, we propose several possible causes for this observation – both the variability from APAM processing or low-temperature microfabrication could mask an underlying trend.In summary, an APAM TFET provides a path toward increasing energy efficiency of transistors by decreasing SS compared to MOSFETs. The process tradeoffs that produce tightly confined 2D doped layers compared to low defect materials are starting to be explored using PMOS devices. Here, we report on the impact of process variability in drawing conclusions from these devices toward the realization of an APAM TFET.SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525.[1] R. H. Dennard et al., “Design of ion-implanted MOSFET's with very small physical dimensions”, IEEE J. Solid-State Circuits 9, 256 (1974).[2] https://irds.ieee.org/[3] J. Koga et al., “Negative differential conductance in three‐terminal silicon tunneling device”, Applied Physics Letters, 69, 1435 (1996).[4] T.-M. Lu et al., “Path towards a vertical TFET enabled by atomic precision advanced manufacturing”, 2021 Silicon Nanoelectronics Workshop (2021).[5] X. Gao et al., “Modeling and Assessment of Atomic Precision Advanced Manufacturing (APAM) Enabled Vertical Tunneling Field Effect Transistor”, 2021 SISPAD, 102 (2021).[6] H. Lu et al., “Tunnel Field-Effect Transistors: State-of-the-Art”, IEEE J. Electron Device Society, 2, 44 (2014).[7] S. Misra et al., “Method of chemical doping that uses CMOS-compatible processes”, U.S. Patent 11,798,808. Figure 1