Range Of Doping Concentrations Research Articles

Doping profiling of beveled Si wafers via UV-micro Raman spectroscopy

Doping profiling methods are required to provide doping monitoring of heavy doped Silicon wafers, widely used in electronic devices, with high concentration sensitivity and spatial resolution. Herein, we demonstrate that ultraviolet (UV) micro-Raman spectroscopy implemented on small-angle beveled surfaces is able to produce a Raman-based doping profile without any further measurements. The reliability of the approach is verified on ion-implanted p-type B-doped single-crystalline Si (100) wafers with shallow (100 nm) doping profile, directly comparing the Raman-based doping profiling results with independent secondary ion mass spectrometry (SIMS) and spreading resistance profiling (SRP) measurements. The Raman-based technique is capable to fully reproduce the doping profile down to 100 nm with excellent doping sensitivity (10 ppm) in the 1018–1020 cm−3 doping concentration range providing high lateral (vertical) resolution of 1μm (10 nm). The technique is comparable to SIMS in terms of resolution and sensitivity down to 1018 cm−3 concentration but requires the beveling process. Instead, it is a better alternative to SRP on bevel due to its higher spatial resolution and avoiding probe contact. The Raman-based doping profiling technique is, therefore, suitable for heavy doped Si with typical shallow doping profiles of state-of-the-art Si-based nanoelectronics.

Mo-Doped SnO2 Quantum Dots Dispersed Over Reduced Graphene Oxide Sheets as an Efficient Anode Material

Abstract We explore the effect of Mo doping over the large enhancement of electrochemical property of Mo-doped SnO2 quantum dots (3–5 nm) grown over rGO (reduced graphene oxide) sheets by a soft chemical process in ambient conditions. The composites were prepared over a range of Mo doping concentrations (0–10%) and 5% Mo doping had achieved the best energy storage characteristics. The capacity of the active material could reach ∼851 mAh g−1 (@ 78 mA g−1) in the beginning and that retained ∼89% (∼758 mAh g−1) with superior cyclic stability (100 cycles) and rate capability (506 mAh g−1 @ ∼1.5 A g−1). The addition of the reductant of 0.06 mol during the synthesis procedure led to further improvement of the capacity to ∼875 mAh g−1 (∼92% retention) and the rate capability (∼587 mAh g−1). These impressive results are ascribed to the distribution of Mo-doped SnO2 QDs, doping of Mo6+ at Sn4+ lattice sites providing more electrons for easy electrical transport, reduction of GO (graphene oxide) to rGO. Mo doping led to the decline in the charge transfer resistance (Rct) from 14.99 Ω for un-doped SnO2/rGO to 14.09 Ω (2.5%), 11.61 Ω (5%), and 11.4 Ω (10%) and promote the electrochemical property of the composite. A simple room-temperature synthesis process was used to produce Mo-doped SnO2/rGO nanocomposite and can be employed for the production of many other oxides and their composites for interesting applications.

Low‐Threshold Lasing from Copper‐Doped CdSe Colloidal Quantum Wells

AbstractTransition metal doped colloidal nanomaterials (TMDCNMs) have recently attracted attention as promising nano‐emitters due to dopant‐induced properties. However, despite ample investigations on the steady‐state and dynamic spectroscopy of TMDCNMs, experimental understandings of their performance in stimulated emission regimes are still elusive. Here, the optical gain properties of copper‐doped CdSe colloidal quantum wells (CQWs) are systemically studied with a wide range of dopant concentration for the first time. This work demonstrates that the amplified spontaneous emission (ASE) threshold in copper‐doped CQWs is a competing result between the biexciton formation, which is preferred to achieve population inversion, and the hole trapping which stymies the population inversion. An optimum amount of copper dopants enables the lowest ASE threshold of ≈7 µJ cm−2, about 8‐fold reduction from that in undoped CQWs (≈58 µJ cm−2) under sub‐nanosecond pulse excitation. Finally, a copper‐doped CQW film embedded in a vertical cavity surface‐emitting laser (VCSEL) structure yields an ultralow lasing threshold of 4.1 µJ cm−2. Exploiting optical gain from TMDCNMs may help to further boost the performance of colloidal‐based lasers.

γ-phase inclusions as common structural defects in alloyed β-(AlxGa1−x)2O3 and doped β-Ga2O3 films

β-Ga2O3 is a promising ultra-wide bandgap semiconductor whose properties can be further enhanced by alloying with Al. Here, using atomic-resolution scanning transmission electron microscopy, we find the thermodynamically unstable γ-phase is a ubiquitous structural defect in both β-(AlxGa1−x)2O3 films and doped β-Ga2O3 films grown by molecular beam epitaxy. For undoped β-(AlxGa1−x)2O3 films, we observe γ-phase inclusions between nucleating islands of the β-phase at lower growth temperatures (∼500–600 °C). In doped β-Ga2O3, a thin layer of the γ-phase is observed on the surfaces of films grown with a wide range of n-type dopants and dopant concentrations. The thickness of the γ-phase layer was most strongly correlated with the growth temperature, peaking at about 600 °C. Ga interstitials are observed in the β-phase, especially near the interface with the γ-phase. By imaging the same region of the surface of a Sn-doped β-(AlxGa1−x)2O3 after ex situ heating up to 400 °C, a γ-phase region is observed to grow above the initial surface, accompanied by a decrease in Ga interstitials in the β-phase. This suggests that the diffusion of Ga interstitials toward the surface is likely the mechanism for growth of the surface γ-phase and more generally that the more-open γ-phase may offer diffusion pathways to be a kinetically favored and early forming phase in the growth of Ga2O3. However, more modeling and simulation of the γ-phase and the interstitials are needed to understand the energetics and kinetics, the impact on electronic properties, and how to control them.

Photochemical transformation of diketone dopants in polyester matrices: Effect of dopants concentration and polyester structure on changes in molecular characteristics and hydrolysis of the matrices

Photochemical transformations of photoactive diketone derivatives, 1,2-diphenylethane-1,2-dione (benzil, BZ) and 1,4-bis(benzoylcarbonyl)benzene (bisbenzil, BIS), and the effects of their transformations on changes in the molecular characteristics and hydrolytic properties of poly(ε-caprolactone) (PCL) and polylactide (PLA) matrices are reported. Studies were performed in a broad dopant concentration range of 0.2–7.5 wt%. Structural changes were observed by FTIR spectroscopy. FTIR spectroscopy proved the progressive transformation of BZ to benzoyl peroxides and, in the case of PCL, the formation of polar groups. Changes in molecular characteristics were observed in GPC traces. Irradiation of the doped polymer films at λ > 400 nm under an air atmosphere resulted mainly in the degradation of the polymer matrices. Additionally, high dopant concentrations in PCL led to partially crosslinked structures with gel contents up to 15%. The photochemical transformation of dopants had a large impact on the PCL matrices compared to that of the PLA matrices. A subsequent hydrolysis process was investigated by determining the extractable products as well as using GPC. Hydrolysis of irradiated PCL samples showed a significant acceleration of hydrolysis compared to that of nonirradiated samples. Furthermore, the hydrolysis rate gradually increased with increasing dopant concentration. The PCL crosslinking and degradation is adjustable by the type of dopant, concentration of dopant and intensity of light during irradiation of PCL. In contrast, a photochemical pretreatment had no observable effect on the hydrolysis of PLA under the investigated conditions.

Theoretical studies on alloying of germanene supported on Al (111) substrate**Project supported by the National Natural Science Foundation of China (Grant No. 11674129).

Using density functional theory, we study the alloying of the buckled hexagonal germanene superlattice supported on Al (111)-(3 × 3), the sheet composed of triangular, rhombic, and pentagonal motifs on Al (111)-(3 × 3), and the buckled geometry on Al (111)-()(19°), which are denoted, respectively, by BHS, TRP, and SRT7, to facilitate the discussion in this paper. They could be alloyed in the low doping concentration range. The stable configurations BHS, TRP, and SRT7 of the pure and alloyed germanenes supported on both Al (111) and its Al2Ge surface alloy, except the SRT7 pure germanene on Al2Ge, could re-produce the experimental scanning tunneling microscopy images. The relatively stable Al–Ge alloy species are the Al3Ge5 BHS-2T, Al3Ge5 TRP-2T, and Al3Ge3 SRT7-1T on Al (111) while they are the Al4Ge4 BHS-1T, Al3Ge5 TRP-2T, and Al27Ge27 SRT7-(3 × 3)-9T on Al2Ge (the n in the nT means that there are n Ge atoms per unit which sit at the top sites and protrude upward). In addition, the Al3Ge5 BHS-2T and Al4Ge4 BHS-1T are the most stable alloy sheets on Al (111) and Al2Ge, respectively. Comparing with the experimental studies, there exists no structural transition among these alloyed configurations, which suggests that the experimental conditions play a crucial role in selectively growing the pure or the alloyed germanene sheets, which may also help grow the one-atomic thick honeycomb structure on idea Al (111).

An insight into the low doping efficiency of Al in sol–gel-derived ZnO:Al films: role of the dopant chemical state

We prepared aluminum-doped zinc oxide (ZnO:Al, AZO) films by a sol–gel method and investigated the effect of doping on the electrical properties of AZO films in the Al doping concentration range of 0.5–3.0 at.%. The negative effect of Al dopants on the carrier mobility counteracted their positive effect on the carrier concentration and the resistivity of the films remained almost constant at the optimum Al doping level of 0.5 at.%. Moreover, the doping efficiency of Al dopant decreased with increasing doping level and the maximum efficiency was not higher than 50% even at the optimum doping concentration. The microstructure and chemical composition of the films were examined by X-ray diffraction, scanning electron microscopy and X-ray photoelectron spectroscopy to elucidate the mechanism behind the low doping efficiency of Al dopant in the sol–gel-derived AZO films. The reason was attributed to the passivation of the dopant in two forms, defect complex nAlZn–VZn originating from the dopant–defect reaction in the ZnO grains and aluminum oxide phase segregating at the ZnO grain boundaries.

Resistances and ESD Reliability Study of Core-Shell Channel Junctionless DG MOSFET

In this article, an investigation has been done to address the resistance and reliability issues with Conventional Double Gate Metal-Oxide-Semiconductor Field-Effect Transistor (Conv. JL DG MOSFET). Due to the uniform doping (concentration range is 1 × 1018 cm−3-1 × 1019 cm−3) in Conv. JL DG MOSFET, the contact resistance at source and drain region is large which degrades the performance of devices. The increment in doping of source and drain region reduces the contact resistance but simultaneously it increases leakage in Conv. JL DG MOSFET. To address above mentioned issues, a new architecture has been discussed which is called Core-Shell Channel (CSC) JL DG MOSFET. The CSC JL DG MOSFET is offering low leakage current with highly doped concentration of impurity in source and drain. The first time electrostatic discharge (ESD) reliability investigation has been done for any JL MOSFET and CSC JL DG MOSFET.

Magnetic behavior of Fe-doped zirconia studied by synchrotron radiation measurements and first-principles simulations

Exploiting first-principles simulations and x-ray absorption near edge spectroscopy (XANES) in high magnetic fields, we investigated the magnetic properties of thin films of zirconia doped with Fe impurities. In our ${\mathrm{Zr}}_{1\ensuremath{-}x}{\mathrm{Fe}}_{x}{\mathrm{O}}_{2\ensuremath{-}y}$ samples, grown by atomic layer deposition (ALD), the Fe dopants are uniformly distributed, ranging from diluted ($x\ensuremath{\simeq}2\text{--}3%$) up to high ($x\ensuremath{\simeq}25%$) atomic concentration. By x-ray magnetic circular dichroism (XMCD), we carefully analyzed, for samples having different Fe concentration, the magnetic moments as a function of temperature, in the range from 5 K up to 150 K, studying the best dopant concentration range maximizing the magnetic signal. Surprisingly, the iron magnetic moment measured for diluted concentrations degrades as the concentration of magnetic dopant increases. On the basis of ab initio simulations, we propose that the microscopic mechanisms responsible for the peculiar magnetic properties of this compound can be explained by oxygen-mediated superexchange mechanism between the Fe dopants producing, at high dopant concentration, an antiferromagnetic coupling between two Fe atoms. We identify and discuss the role of O vacancies to control such microscopic mechanisms.

Explicit continuous charge-based compact model of surrounding gate MOSFET (SRGMOSFET) with smooth transition between partially-depleted to fully-depleted operation

A charge-based compact model that includes the dynamic depletion behavior for arbitrary doped surrounding gate MOSFET (SRGMOSFET) is presented in this paper. The one-dimensional Poisson’s equation is first solved to obtain the continuous explicit solution of the mobile charge density and drain current expression. A smooth transition between partially-depleted (PD) and fully-depleted (FD) regions of the channel potential is then obtained by using perturbation approach in deriving its corrected surface potential due to the ionized dopant carrier. This corrected surface potential is used to calculate the bulk charge and subsequently captured the dynamic depletion behavior of the surface potential. The comparison between the analytical model and 2D TCAD simulation demonstrates good agreement not only for a wide range of terminal biases, dopant concentration and geometry sizes, but also captured the characteristics of SRGMOSFET such as volume inversion and smooth transition between PD and FD regions. The surface potential agreed well with numerical TCAD simulation results for dopant-geometry ratio () of approximately 0.9, which is about 50% improvement of accuracy compared to the FD compact models of only at 0.45.

Salient features of SrO doping in Al2O3 – 5 wt.% ZrO2 reaction sintered composite ceramics

SrO doping (concentration range ≈ 5000 ppm) in Al2O3–5 wt.% ZrO2 ceramic system offers the unique features of reaction sintering to produce dense composite ceramics of finer sized matrix grains with nearly homogeneous multiphase microstructures for improving the room-temperature structural properties (e.g. hardness, strength, and toughness). Reaction sintered product, the strontium hexaluminate (SrAl12O19) forms in-situ as an interphase boundary in the ceramic composite during the stages of reaction sintering. This creates new low energy Al2O3/SrAl12O19 chemical interfaces in the matrix of alumina. Typical issues based on prominent role of in-situ formed low energy Al2O3/SrAl12O19 interfaces on the properties of reaction sintered composite ceramics (SrO doped Al2O3–5 wt.% ZrO2) are discussed.

Evolution of a Non-Uniform Deformed State in the Structure of Zinc-Chalcogenide Cubic Crystals Doped by 3d Ions

The real structure of bulk Zn1 – хМхSe (S) crystals of diluted magnetic semiconductors with М = V, Cr, Fe, Co, Ni 3d impurities is characterized by neutron diffraction. These impurities are known to greatly destabilize even the initial lattices of pure zinc chalcogenides. Data on the resulting non-uniform microstrain field induced by atomic displacements are obtained from the structural peaks along the tangential and radial directions on the above crystals within a dopant concentration range of 0.01 ≤ х ≤ 0.10. Additional nodes with q = (1/3 1/3 1/3) 2π/a (q is the wave vector and a is the cubic unit cell) emerging in the reciprocal lattice of the cubic structure are considered as evidence for a pre-transition to the fcc (face-centered cubic)–hcp (hexagonal close-packed) phase state, which implies transitions from the fcc lattice along an 8-ray non-Lifshitz star with the wave vector k5 = μ(b1 + b2 + b3), where b1, b2, b3 are the reciprocal lattice vectors and μ ≈ 1/3.

Defect Structure of Zinc-Doped LiNbO3 Crystals in a Wide Range of Dopant Concentrations

IR absorption spectra of zinc-doped LiNbO3 crystals in the stretching region of OH groups, Raman spectra of the crystals, and their optical absorption spectra provide evidence of drastic changes in the mechanism responsible for the incorporation of Zn into the structure of the crystals and the nature of hydrogen bonds and the corresponding proton-containing charged defect complexes ( $$V_{{{\text{Li}}}}^{ - }$$ –OH–, NbLi–OH−, and $${\text{Zn}}_{{{\text{Nb}}}}^{{{\text{3}} - }}$$ –OH−) near a concentration threshold at ≈6.76 mol % ZnO in the melt.

Enhanced Gilbert damping in Re-doped FeCo films: Combined experimental and theoretical study

The effects of rhenium doping in the range 0 to 10 atomic percent on the static and dynamic magnetic properties of Fe65Co35 thin films have been studied experimentally as well as with first principles electronic structure calculations focusing on the change of the saturation magnetization and the Gilbert damping parameter. Both experimental and theoretical results show that the saturation magnetization decreases with increasing Re doping level, while at the same time Gilbert damping parameter increases. The experimental low temperature saturation magnetic induction exhibits a 29 percent decrease, from 2.31 T to 1.64 T, in the investigated doping concentration range, which is more than predicted by the theoretical calculations. The room temperature value of the damping parameter obtained from ferromagnetic resonance measurements, correcting for extrinsic contributions to the damping, is for the undoped sample 0.0027, which is close to the theoretically calculated Gilbert damping parameter. With 10 atomic percent Re doping, the damping parameter increases to 0.0090, which is in good agreement with the theoretical value of 0.0073. The increase in damping parameter with Re doping is explained by the increase in density of states at Fermi level, mostly contributed by the spin-up channel of Re. Moreover, both experimental and theoretical values for the damping parameter are observed to be weakly decreasing with decreasing temperature.

Tuning infrared plasmon resonances in doped metal-oxide nanocrystals through cation-exchange reactions

Metal-oxide nanocrystals doped with aliovalent atoms can exhibit tunable infrared localized surface plasmon resonances (LSPRs). Yet, the range of dopant types and concentrations remains limited for many metal-oxide hosts, largely because of the difficulty in establishing reaction kinetics that favors dopant incorporation by using the co-thermolysis method. Here we develop cation-exchange reactions to introduce p-type dopants (Cu+, Ag+, etc.) into n-type metal-oxide nanocrystals, producing programmable LSPR redshifts due to dopant compensation. We further demonstrate that enhanced n-type doping can be realized via sequential cation-exchange reactions mediated by the Cu+ ions. Cation-exchange transformations add a new dimension to the design of plasmonic nanocrystals, allowing preformed nanocrystals to be used as templates to create compositionally diverse nanocrystals with well-defined LSPR characteristics. The ability to tailor the doping profile postsynthetically opens the door to a multitude of opportunities to deepen our understanding of the relationship between local structure and LSPR properties.

Annealing induced transformation and enhancement in the electronic defect states of Al doped ZnO films and their correlation with the optoelectronic properties

In this study, we report the transformation and/or enhancement of the electronic defect states by performing several annealing experiments on the same samples. To this end, Al-doped ZnO (AZO) films on the soda lime glass substrates were deposited by using sol-gel followed by spin coating process and then subjected to various annealing conditions at different pressure, like, air, low vacuum (1 × 10−2 mbar) and/or high vacuum (1 × 10−6 mbar); each at 500 °C for 1 h. A wide range of experimental techniques was used to characterize the overall microstructure and optoelectronic properties of these films after each annealing stage. Though the overall microstructure of all these films are found to change only marginally, the electronic defect states are found to significantly alter because of these repetitive annealing, leading substantial change in their electrical properties and also affecting these optically. Moreover, the effectiveness of Al doping is found to increase significantly because of the second annealing step, leading an increase in carrier concentration in all these films for a wider range of initial dopant concentration (0.0–3.0 at. %).

Structural evolution and phase diagram of the superconducting iron selenides Li x (C2H8N2) y Fe2Se2(x= 0 ~ 0.8).

Here we report on the structural and electronic phase diagram of lithium and ethylenediamine intercalated FeSe in a wide range of dopant concentration . Undoped crystallizes in an orthorhombic phase. With increasing lithium doping, an orthorhombic to tetragonal phase transition occurs at , and the superconducting tetragonal phase persists until . Meanwhile, the is found dependent strongly on dopant concentration, raising rapidly from 30 K at to 45 K at . The crystal structures of are determined by using high-resolution neutron diffraction data at 5, 60, 150, and 295 K, respectively. The distortion of the FeSe tetrahedron is enhanced significantly from 150 to 295 K, meanwhile, the normal-state Hall resistivity changes sign from negative to positive in the same temperature range. The dominant hole carrier in electron-doped above 230 K suggests that the temperature-induced structure distortion may lead to a reconstruction of the Fermi surface topology and the appearance of hole pockets.

Electro-optic properties of singly and doubly doped lithium niobate crystal by rare earth elements for optoelectronic and laser applications

Congruent lithium niobate (LN) doped with rare-earth elements is a promising host for integrated optic combining the properties straightforwardly associated to the dopant with the good electro-optic (EO) properties. By direct technique based on interferometric optical arrangement at a wavelength of 633 nm and at room temperature, we have experimentally determined the figure of merit F = n3reff, (n is the refractive index and reff, the effective EO coefficient) and finally calculated the EO coefficients reff of the third-column of the unclamped EO tensor of three series of singly doped LN with Yb3+, Ho3+, Tm3+ and two series of doubly doped Er3+–Yb3+. It is found that in all the studied opto-geometric configurations, the unclamped figure of merit and consequently the corresponding EO coefficients are relatively constant in the considered dopant concentration range. As the figure of merit, F qualifies crystals for EO modulation and laser applications, all reported results confirm that the LN singly or doubly doped with rare-earth elements are very promising versatile candidates for several multifunctional nonlinear devices in optoelectronic and laser applications.

Molecular beam epitaxy growth and temperature-dependent electrical characterization of carbon-doped GaAs on GaAs(1 1 1)B

Here we present a study of the solid source molecular beam epitaxy growth of carbon doped GaAs(1 1 1)B oriented layers in a wide doping concentration range from 1016 to 1020cm-3. The layers have been fabricated on GaAs(1 1 1)B substrates with a 1° miscut towards (2 1 1) and carbon was supplied by a heated graphite filament source. Atomic force microscopy revealed smooth surfaces (root mean square roughness 0.3 nm) up to the highest carbon concentration. The carbon concentration was determined by secondary ion mass spectroscopy. All samples exhibit p-type conductivity and temperature-dependent Hall- and resistivity measurements show carrier freeze out for doping concentration in the 1016 cm−3 and 1017 cm−3 range, whereas we observe degenerated behavior for carbon concentrations above ca. 1×1019 cm−3. The hole mobility decreases with increasing carbon concentration. The acceptor ionization energy for carbon was determined via low-temperature photoluminescence measurements to 26.3 meV. From the free hole density determined from Hall-measurements at 300 K and the overall carbon concentration, we estimate that approximately 100% of the carbon atoms are electrically active acceptors for carbon concentrations below 1×1018 cm−3. For concentrations above 1×1019 cm−3 compensation sets in and the doping efficiency is well below 100%. For comparison, samples in the standard (1 0 0)-orientation have been produced and carbon incorporation behavior during growth is very similar.

Synthesis and characterization of Fe-doped ZnO thin films deposited by chemical spray pyrolysis

In the present study, iron doped zinc oxide (ZnO : Fe) thin films were prepared by using a simple chemical spray pyrolysis technique by varying the doping concentration in the range, 0–6 at.% at a constant substrate temperature of 400 °C.The effect of Fe-doping concentration on the physical behavior of ZnO thin films were analyzed and discussed. The X-ray diffraction (XRD) patterns exhibited hexagonal wurtzite crystal structure without any secondary phases for all the films irrespective of the doping concentration. However, the preferential orientation changed from (002) to (101) plane with increase of Fe-doping. The Raman spectroscopy studies showed the peaks at 338 cm-1, 438 cm-1 and 574 cm-1 which are the characteristic vibrational modes of ZnO. The scanning electron microscopic (SEM) images showed irregular shaped grains grown over the substrate surface. The X-ray photoelectron spectroscopy (XPS) studies confirmed the presence of Fe in 3+ state in ZnO layers. The Fourier transform infrared (FTIR) spectroscopy data revealed the presence of iron in the doped ZnO films by showing the modes related to iron in addition to ZnO. The optical properties revealed that the films with lower Fe-doping concentration (≤ 2 at.%) showed high transmittance and wide band gap than the pure and highly Fe-doped ZnO films. The evaluated band gap showed a red shift upon doping with the energy band gap decreased from 3.24 eV to 3.01 eV for the investigated doping concentration range. The photoluminescence spectra also showed similar optical behavior with quenching of PL signal intensity of the films. Moreover, all the Fe-doped ZnO films showed ferromagnetic behavior at room temperature.