Surface State Density Research Articles

Accumulation and Erase of Radiation-Induced Charge in MOS Structures

It is shown that when a MOS (metal–oxide–semiconductor) structure is simultaneously exposed to radiation and high-field injection of electrons, part of the radiation-induced positive charge can be erased when interacting with injected electrons, and the density of surface states can increase. These phenomena must be taken into account when operating MOS radiation sensors in high-field charge injection modes. High-field injection modes used for post-radiation erase of positive charge in MOS sensors are analyzed. It has been established that to annihilate one hole (radiation-induced positive charge), it is necessary to inject (0.5–2) × 104 electrons into the gate dielectric; the magnitude of the electric field has almost no effect on the process of erasing the radiation-induced charge.

Effect of N2-H2 remote plasma nitridation temperature on surface properties of Te-doped GaSb crystals

GaSb is regarded as one of the most promising near-infrared optoelectronic materials in recent years. However, due to the ease of natural oxidation of GaSb, the surface will promptly form a thick oxide layer which is highly resistant to removal, resulting in detrimental interface defects and higher surface state density. Although studies have demonstrated the feasibility of plasma for removing oxide, the ultra-high vacuum is necessary for complete removal, which poses challenges for commercial applications. Herein, we optimized the nitrogen plasma passivation process for Te-doped GaSb, combining remote plasma source with Atomic Layer Deposition (ALD) in-situ annealing to modify GaSb (001) surface, which approaches non-damaging treatment. The temperature during passivation will affect nitrogenation on GaSb surface, result in enrichment of metallic Sb when reaching 573 K, and impact emission efficiency. By setting the passivation temperature at 523 K and combining with in-situ annealing, the photoluminescence (PL) efficiency of GaSb has doubled. This demonstrates the validity of low-temperature nitrogen passivation in improving surface state and reducing defect density on GaSb.

Modeling influence of temperature and magnetic field on the density of surface states in semiconductor structures

Modeling influence of temperature and magnetic field on the density of surface states in semiconductor structures

Massive Onset Potential Shifting with an Epitaxial GaAs/Si Photocathode for Solar H2 Production

Solar photoelectrochemical (PEC) H2 production has the potential to solve one of the biggest issues confronting humanity nowadays: producing inexpensive, clean and renewable energy. Among various semiconductor materials, GaAs is an excellent candidate for the development of photoelectrodes within PEC cells for unassisted solar water splitting thanks to its appropriate band gap, good transport and optical properties and high quantum yield. However, the main limitations of GaAs photoelectrodes are related to the high substrate cost, their huge overpotentials and the short lifetime under operation. To address these issues, in this work, we report on the photocathode performance of 1 µm-thick GaAs layers grown on a low-cost Si p-doped substrate by MBE (Molecular Beam Epitaxy) and compare them to those of GaAs:p doped wafers . The photocathodes were investigated in 0.2 M H2SO4 (aq) electrolyte under 1 sun (100 mW/cm2) illumination. The onset potential (Vonset) of bare GaAs/Si and bare GaAs:p wafer is quite comparable, at around -0.2 V vs reversible hydrogen electrode (RHE). The significant reduction of surface states density with a sulfur passivation (S-passivation) by immersing samples in (NH4)2S solution is demonstrated but with very limited changes on the Vonset value, for both GaAs:p wafer and GaAs/Si photocathodes. In contrast, the deposition of thin Pt catalyst layers on both photocathodes by electroless deposition technique leads to a large positive shift Vonset. The Vonset of GaAs/Si and GaAs:p wafer photocathodes are increased up to 0.34 and 0.15 V vs RHE respectively. We show that the Vonset of GaAs/Si can be even improved by combining the Pt catalyst and the S-passivation process, reaching 0.4 V vs RHE (Fig. 1), a record value for GaAs-based Schottky-like photocathodes.STEM-EDX analysis was performed to investigate further the difference between Pt/GaAs/Si and Pt/GaAs:p wafer photocathodes. The EDX-line scans show that after the Pt electroless deposition, the Pt layer on GaAs:p wafer is homogeneous and shows an As0-rich Pt surface that can explain the weaker catalytic activity in comparison with GaAs/Si. Indeed, for the latter, Pt is deposited inhomogenously in the form of clusters leaving some bare surface. Here, As0 is expected to be more easily removed from the surface during the electroless deposition, resulting in more efficient catalyst properties of Pt. The morphology differences between the two Pt-coated electrodes are confirmed by XPS measurements. Since the process of electroless deposition strongly depends on the doping concentration of the materials deposited, the difference between GaAs:p wafer and GaAs/Si photocathodes is attributed to variations in their doping concentrations. Furthermore, the inhomogeneity of the Pt coating on GaAs/Si can also benefit to the passivation process by allowing the (NH4)2S solution to reduce more efficiently the surface defects at the oxide/semiconductor interface. Finally, the stability of Pt/GaAs/Si photocathodes was evaluated, and a lifetime larger than 112 h was established. These findings provide guidance for further studies towards the fabrication of scalable, cost-efficient and stable unassisted PEC cells for green hydrogen production. This research is supported by the “France 2030” French National Research Agency NAUTILUS Project (Grant no. ANR-22-PEHY-0013). Figure 1

Electrochemistry and DFT study of galvanic interaction on the surface of monoclinic pyrrhotite (0 0 1) and galena (1 0 0)

The electrochemical interaction between galena and monoclinic pyrrhotite was investigated to examine its impact on the physical and chemical properties of the mineral micro-surface. This investigation employed techniques such as electrochemistry, metal ion stripping, X-ray photoelectron spectroscopy, and quantum chemistry. The electrochemical test results demonstrate that the galena surface in the electro-couple system exhibits a lower electrostatic potential and higher electrochemical activity compared to the monoclinic pyrrhotite surface, rendering it more susceptible to oxidation dissolution. Monoclinic pyrrhotite significantly amplifies the corrosion rate of the galena surface. Mulliken charge population calculations indicate that electrons are consistently transferred from galena to monoclinic pyrrhotite, with the number of electron transfers on the mineral surface increasing as the interaction distance decreases. The analysis of state density revealed a shift in the surface state density of galena towards lower energy levels, resulting in decreased reactivity and increased difficulty for the reagent to adsorb onto the mineral surface. Conversely, monoclinic pyrrhotite exhibited an opposite trend. The XPS test results indicate that galvanic interaction leads to the formation of hydrophilic substances, PbSxOy and Pb(OH)2, on the surface of galena. Additionally, the surface of monoclinic pyrrhotite not only adsorbs Pb2+ but also undergoes S0 formation, thereby augmenting its hydrophobic nature.

Enhanced electrical parameters of the Au/n-Si Schottky barrier diodes with graphite/graphane oxide doped PVC interlayer

In this work, Schottky Barrier diodes (SBDs) formed on n-Si substrates were created using polyvinyl-chloride (PVC) and graphite/graphene-oxide (Gt/GO) nanoparticles (NPs) doped PVC interlayers and the conduction mechanisms of the structures were compared to the reference Au/n-Si (MS) diode. The characterization methods, including x-Ray Diffraction (XRD), Field Emission Scanning Electron Microscope (FE-SEM), and Energy Dispersive x-Ray (EDX), were used to analyze Gt/GO NPs and examine their structural, morphological, and analytical properties. In addition to the standard I-V method, modified Norde and Cheung methods were applied to analyze the forward bias I-V characteristics to determine the impact of pure-PVC and (PVC: Gt-GO) interlayers’ main electronic parameters on the SBDs. The surface state density (N ss ) depending on energy was also determined from the forward bias current–voltage by considering the voltage-dependent ideality coefficient, n(V), and barrier height (BH), ΦB(V). The outcomes showed that, as compared to MS structures, both the pure-PVC and (PVC: Gt-GO) interlayer leads to a decrease of n, leakage-current, N ss , an increase of rectification ratio (RR), shunt-resistance (R sh ) and zero-bias barrier-height (Φ B0 ). The differences in the electronic parameters observed between the I-V, Norde, and Cheung functions indicate that these parameters are highly reliant on the voltage and the computation method utilized. The barrier inhomogeneities at the metal/semiconductor surface also affect the current-transport or conduction mechanisms.

Electric and dielectric responses of Au/n-Si structure by Mn doped PVC interfacial layers

This paper has investigated and compared the impact of polyvinyl chloride (PVC) without/with manganese (Mn) metallic nanoparticles interfacial layer on the electric and impedance characteristics of Schottky diode (SD) with a structure of Au/n-Si (MS). The structures of these two metal-polymer-semiconductor (MPS) SDs are Au/PVC/n-Si and Au/PVC:Mn/n-Si. A detailed description of the SDs manufacturing process is given. The x-ray diffraction (XRD) analysis, Scanning Electron Microscope (FE-SEM) images, and Electron Dispersive x-ray (EDX) spectroscopy are three methods that have been utilized to examine mean size of crystallite, morphology of surface, purity specification. The fundamental electronic variables of these devices are ascertained and contrasted with one another using the I-V characteristic measurement at ±6 V. Ohm’s law, Thermionic Emission (TE) theory, modified Norde, and Cheung functions are used to calculate the SDs’ leakage current (I0), ideality coefficient (n), potential barrier height (BH), shunt (Rsh), and series (Rs) resistances. Investigations are conducted on the energy dependence of surface states density (Nss) and the current conduction mechanisms (CCMs) for both reverse and forward biases. These interfacial layers are known to decrease the n, Rs, and Nss. The PVC polymer interlayer leads to improve the efficiency of the MS-type SD, but it does not when doped by Mn nanoparticles. Additionally, by measuring impedance at a bias of 1.5 V and 100 Hz-1 MHz frequency range, the frequency dependence of dielectric properties of the prepared SDs is studied. The dielectric permittivity, dielectric loss tangent, electronic modulus, and ac electronic conductivity of these SDs are all studied.

A high sensitivity temperature coefficient of the Au/n-Si with (CdTe-PVA) structure based on capacitance/conductance-voltage (C/G-V) measurements in a wide range of temperature

This study focused on revealing the temperature-sensing performance and rudimental electrical-properties of the Au/(CdTe-PVA)/n-Si depending on the temperature via impedance-measurements. The temperature-sensitivity (S) for constant-capacitance drive mode shows two-distinct linear-regions corresponding to low/moderate temperatures. The highest S value was achieved as 15.5 mV/K at 0.60 nF value. Nicollian-Brews and Hill-Coleman methods were applied to determine series-resistance (RS) and density of surface-states (NSS) values. The low RS values and the proper magnitude of NSS demonstrate the high quality and performance of the Au/(CdTe-PVA)/n-Si. Additionally, the electrical parameters obtained from C-2-V plots show almost temperature-independent behavior at moderate temperature regions. The low activation-energy values (Ea) determined via Arrhenius-plot indicate hopping of the trapped electron from trap to trap or conduction band dominates the ac conduction. In conclusion, the variations of electrical-parameters and the high S value consolidate the usability of Au/(CdTe-PVA)/n-Si as a thermal sensor in the low-temperature regions.

High-output ∼3 μ m MIR pulsed laser enabled by surface state regulation in PtTe2 optical switch

Mid-infrared (MIR) pulsed lasers operating in the ∼3 μm region play a crucial role in various applications, including molecular spectroscopy, ultrafast molecular imaging, and laser-assisted surgery. Despite recent advancements in MIR gain platforms, a notable technological challenge remains in the absence of an effective optical Q-switch. Here, a remarkable optical Q-switch in the 3 μm region based on a Dirac semimetal PtTe2 saturable absorber is realized. By modulating the surface state of PtTe2, the pulsed laser exhibited an increase in average power, escalating from 521 to 588 mW, accompanied by a significant decrease in pulse width from 368 to 187 ns. Nondegenerate pump–probe measurements showed that the recombination rate of the photocarrier in thinner PtTe2 nanoplates was effectively accelerated, primarily attributed to the substantial increase in surface state density, leading to better saturable absorption performance. As the thickness of the PtTe2 nanoplates decreases, the nonsaturable loss decreases from 12% to 3%, while the modulation depth increases from 6% to 12%. The enhanced ultrafast nonlinear absorption enables flexible modulation of saturation absorption parameters, which endows high-performance MIR pulsed laser generation.

Picosecond carrier dynamics in InAs and GaAs revealed by ultrafast electron microscopy.

Understanding the limits of spatiotemporal carrier dynamics, especially in III-V semiconductors, is key to designing ultrafast and ultrasmall optoelectronic components. However, identifying such limits and the properties controlling them has been elusive. Here, using scanning ultrafast electron microscopy, in bulk n-GaAs and p-InAs, we simultaneously measure picosecond carrier dynamics along with three related quantities: subsurface band bending, above-surface vacuum potentials, and surface trap densities. We make two unexpected observations. First, we uncover a negative-time contrast in secondary electrons resulting from an interplay among these quantities. Second, despite dopant concentrations and surface state densities differing by many orders of magnitude between the two materials, their carrier dynamics, measured by photoexcited band bending and filling of surface states, occur at a seemingly common timescale of about 100 ps. This observation may indicate fundamental kinetic limits tied to a multitude of material and surface properties of optoelectronic III-V semiconductors and highlights the need for techniques that simultaneously measure electro-optical kinetic properties.

Impact of Surface States in Graphene/p-Si Schottky Diodes.

Graphene-silicon Schottky diodes are intriguing devices that straddle the border between classical models and two-dimensional ones. Many papers have been published in recent years studying their operation based on the classical model developed for metal-silicon Schottky diodes. However, the results obtained for diode parameters vary widely in some cases showing very large deviations with respect to the expected range. This indicates that our understanding of their operation remains incomplete. When modeling these devices, certain aspects strictly connected with the quantum mechanical features of both graphene and the interface with silicon play a crucial role and must be considered. In particular, the dependence of the graphene Fermi level on carrier density, the relation of the latter with the density of surface states in silicon and the coupling between in-plane and out-of-plane dynamics in graphene are key aspects for the interpretation of their behavior. Within the thermionic regime, we estimate the zero-bias Schottky barrier height and the density of silicon surface states in graphene/type-p silicon diodes by adapting a kown model and extracting ideality index values close to unity. The ohmic regime, beyond the flat band potential, is modeled with an empirical law, and the current density appears to be roughly proportional to the electric field at the silicon interface; moreover, the graphene-to-silicon electron tunneling efficiency drops significantly in the transition from the thermionic to ohmic regime. We attribute these facts to (donor) silicon surface states, which tend to be empty in the ohmic regime.

Engineering surface state density of monolayer CVD grown 2D MoS2 for enhanced photodetector performance.

This study demonstrates the effect of nitrogen doping on the surface state densities (Nss) of monolayer MoS2 and its effect on the responsivity and the response time of the photodetector. Our experimental results shows that by doping monolayer MoS2 by nitrogen, the surface state (Nss) increases thereby increasing responsivity. The mathematical model included in the paper supports the relation of photocurrent gain and its dependency on trap level which states that the increasing the trap density increases the photocurrent gain and the same is observed experimentally. The experimental results at room temperature revealed that nitrogen doped MoS2 have a high NSS of 1.63 X 1013 states/m2/eV compared to undoped MoS2 of 4.2 x 1012 states/m2/eV. The increase in Nss in turn is the cause for rise in trap states which eventually increases the value of photo responsivity from 65.12 A/W (undoped MoS2) to 606.3 A/W (nitrogen doped MoS2). The response time calculated for undoped MoS2 was 0.85 sec and for doped MoS2 was 0.35 sec. Finally, to verify the dependence of surface states on the responsivity, the surface states were varied by varying temperature and it was observed that upon increment in temperature, the surface states decreases which causes the responsivity values also to decrease.

Sulfur poisoning-resistant TiO2/Cu-doped ZnIn2S4 photoanode for achieving efficient sulfur oxidation

Ternary ZnIn2S4 is a layered metal sulfide and suitable for catalyzing H2S-containing industrial waste streams due to its excellent light absorption in the visible region. However, imperfect electrical conductivity and slow surface reaction lead to severe internal intrinsic charge recombination. For this reason, we modify pristine ZnIn2S4 by synergistic coordination of heterojunction and doping. The TiO2/0.6 ml Cu2+-ZIS sample achieves a photocurrent density of 2.87 mA/cm2, which is 8.2 times higher than that of pure ZnIn2S4. Investigation of the surface states (SS) shows that the improved performance results from an increase in the density of available surface states as well as the consistency of the surface state center potential with the S/H2S oxidation potential. This is the new attempt to analyze the photoelectrocatalytic (PEC) behavior of the sulfur oxidation reaction using surface state theory. The results of catalytic product resolution and data from theoretical calculations indicate that the timely desorption of polysulfide ions at Cu2+ sites and the solubility of the only oxidation product (S2O32-), are the reasons for maintaining high performance after 4 h stability testing. This study not only gives a new reference for the modification strategy of ZnIn2S4 but also a new solution for catalyst S poisoning.

Preparation of N-Si-P-GaSe Heterojunctions Based on an Amorphous GaSe Layer Without Impurities and Study of Their Electrical Properties

The electrical and photoelectric properties of anisotype n-Si−p-GaSe heterojunctions obtained as a result of the deposition of a GaSe thin layer on a cold n-Si single crystal substrate by the thermal evaporation method were studied. It was determined that the height of the potential barrier in thermal annealing structures at T = 200 °C during t = 3 hours occurs due to the decrease in the density of states of local levels located near the Fermi level in the amorphous layer. The mechanism of photosensitivity in an isotype heterostructures was analyzed and it was found that the photosensitivity of the heterojunction increases as a result of a decrease in the surface density of state at the contact boundary of the components, by thermal means. The spectral distribution of the quantum efficiency in the n‑Si – p‑GaSe heterojunction was studied and their perspective was determined.

Electrical properties of PVC:BN nanocomposite as interfacial layer in metal-semiconductor structure

In this study, a comprehensive examination is assumed to investigate the influence of interfacial layers composed of polyvinyl chloride (PVC) and polyvinyl chloride-boron nitride (PVC: BN) on the electrical characteristics of the Au/n-Si structure. Two distinct structures, namely Au/PVC/n-Si (MPS1) and Au/PVC: BN/n-Si (MPS2), are fabricated for this purpose. The provided boron nitride (BN) nanostructures are analyzed using X-ray diffraction (XRD) patterns to determine their average crystalline size and surface morphology. Following the structural analysis, current-voltage (I–V) measurements are conducted over an extensive voltage range (± 3 V). Subsequently, the fundamental electrical properties of the developed Schottky structures are determined using various methods and compared. Experimental results indicate that the PVC: BN nanocomposite leads to an increase in the potential barrier height (BH), shunt resistance (Rsh), and rectifying rate (RR = IF/IR), while simultaneously decreasing the ideality factor (n), series resistance (Rs), and surface states density (Nss). It was discovered that the MS structure’s RR was 7 times lower than that of the MPS2 structure. Moreover, the energy-dependent Nss density is also derived using n(V) and ΦB0(V) functions. Based on the ln(IR)−VR0.5 profile at the reverse bias region, the Schottky-emission (SE) type conduction mechanism is effective for MS structures, whereas Poole-Frenkel-emission (PFE) is effective for MPS structures.

Frequency-dependent physical parameters, the voltage-dependent profile of surface traps, and their lifetime of Au/(ZnCdS-GO:PVP)/n-Si structures by using the conductance method

In this study, frequency-dependent physical parameters, voltage-dependent of surface traps/states, and their lifetime of the Au/(ZnCdS-GO:PVP)/n-Si (MPS) type structures were investigated by using conductance measurements (Y = 1/Z = G + jωC) both in wide range frequency (3 kHz-3 MHz) and voltage (from − 4.00 V to 1.50 V). Firstly, basic physical parameters such as density of doping donor atoms (ND), diffusion potential (VD), Fermi-energy (EF), barrier height ΦB(C-V), depletion-layer thickness (WD), and maximum electric field (Em) were calculated from these measurements for each frequency. These values were found as 1.69 × 1016 cm−3, 0.444 eV, 0.193 eV, 0.606 eV, 1.31 × 10−5 cm, 7.66 × 104 V/cm for 10 kHz, and 1.42 × 1016 cm−3, 0.461 eV, 0.198 eV, 0.628 eV, 1.46 × 10−5 cm, 7.80 × 104 V/cm for 3 MHz, respectively. While ND decreases with increasing frequency, the other parameters increase. The density of surface states (Nss) and their lifetimes (τ) were also obtained from conductance techniques. While the Nss were changed between 2.78 × 1012 at 0.40 V and 2.61 × 1012 eV-1cm−2 at 1.3 V, and the Nss-V curve shows two distinctive peaks which correspond to 0.5 V (2.87 × 1012 eV−1cm−2) and 1.2 V (2.68 × 1012 eV−1cm−2), respectively. The values of τ were changed between 105 µs (at 0.4 V) and 15.3 µs (at 1.3 V) and decreased with increasing voltage as exponentially. These lower values of Nss were attributed to the used (ZnCdS-GO:PVP) interlayer.

Electrochemistry at 2D and 3D nanoelectrodes: The interplay between interface kinetics and surface density of states

Heterogenous Electron Transfer (HET) at electrode-electrolyte interfaces depends strongly on the morphological features or geometry of the nanostructure used for modifying the electrode surface. A swift HET results in faster interface kinetics, which has significant impact on the development/calibration of electrochemical devices like biomolecular sensors, supercapacitors, batteries and electrochromic platforms. The interface electrochemistry depends strongly on the electronic Density of States (DOS) of electrode materials. Over the past years, the 2D electron gas nanomaterials - primarily graphene, Graphene Oxide (GO) and Reduced Graphene Oxide (RGO), have garnered significant interest in electrochemical applications due to promising DOS features. However, the electroanalytical dependency on DOS of 3D nanostructures such as Zinc Oxide Tetrapods (ZnOT) is yet unexplored. The current work focusses on a comparative electrochemical analysis of interface kinetics at RGO (2D) and ZnOT (3D) coated screen printed electrodes, with the intention of selecting the suitable material geometry. The analyses were performed using Cyclic Voltammetry (CV) and Electrochemical Impedance Spectroscopy (EIS). While the dependence of HET on DOS of RGO and ZnOT nanomaterials were studied using both DFT analysis and impedance-derived capacitance spectroscopy – the latter giving insights on quantum capacitance. It was observed that, the 2D RGO nanostructures exhibit higher surface DOS near the Fermi level, along with a high quantum capacitance (∼345 nF) as compared to 3D ZnOT (∼276 nF). This results in enhanced HET at the former, thereby indicating its suitability in developing futuristic electrochemical devices for various applications as desired.

Characterization of the electrical properties of MPS schottky structures incorporating Fe doped polyvinyl chloride (PVC)

This paper explores the effects of the organic interfacial layer on the electrophysical characteristics of Schottky barrier diodes (SBDs). Three types of SBDs were fabricated: Au-Si (referred to as MS), Au/PVC/Si (referred to as MPS1), and Au-/PVC:Fe/Si (referred to as MPS2). Fe nanopowders were subjected to analysis using XRD, SEM, and EDX techniques to investigate their structural and optical characteristics. To investigate the conduction mechanisms of these diodes, I-V characteristics were examined using thermionic-emission (TE), Cheung, and Norde functions. The surface-state density (N ss ) distribution of energy was determined by analyzing the current–voltage (IF-VF) curve under forward bias conditions. This analysis considered the voltage-dependent barrier height (BH) and ideality factor (n(V)). The results demonstrated that the polymeric interlayer without Fe nanoparticles reduced N ss by a factor of 7, while the presence of Fe nanoparticles led to a two-order magnitude decrease, resulting in improved efficiency in comparison with MS structures. The obtained results indicated that including a polymeric layer in MPS structure enhanced their electrophysical features compared to MS diodes, and significantly increased rectification by 15–45 times. In summary, the existence of an organic interfacial layer significantly altered the conduction mechanisms and electrophysical characteristics of MPS diodes. It was found that the addition of Fe nanoparticles in the interlayer resulted in substantial improvements in N ss , efficiency, rectification, and conduction characteristics compared to MS diodes.

Synergistic boost of catalytic activity in ZrTe topological catalyst via multiple topologically-electronic states

Topological materials feature highly-active topological surface states and high carrier mobility, making them promising catalysts. While ongoing research centers on topological catalysis, most topological semimetal catalysts tend to showcase either a singular topological electronic state or a lone highly catalytic surface, imposing limitations on overall efficiency. Our study highlights ZrTe as a standout catalyst for hydrogen evolution, boasting multiple topological states that excel across various surfaces. ZrTe exhibits a Weyl nodal ring and a triple degenerate nodal point near the Fermi energy, resulting in topological surface states on multiple surfaces. Notably, the (010) and (001) surfaces exhibit remarkable catalytic performance, with Gibbs free energy (ΔGH*) values surpassing that of the Pt metal. Our work establishes a robust and unequivocal link between catalysis and topological properties on the catalytic surfaces, revealing a linear correlation between ΔGH* and topological surface state density. ZrTe emerges as an exceptional topological catalyst, with both of its topological states significantly contributing to the catalytic performance on distinct surfaces. This pioneering discovery offers a valuable platform for advancing catalyst research in the concept of topological catalysts.

On the Properties of the Si-SiO2 Transition Layer in Multilayer Silicon Structures

Capacitance spectroscopy was used to study the capacitive-voltage characteristics of multilayer structures with a Si-SiO2 transition layer in Al-SiO2-n-Si type samples fabricated by the thermal oxidation of a semiconductor. It is shown that the inhomogeneous distribution of the density of surface states is a localized electroactive center at the very semiconductor-dielectric interface, due to over-barrier charge emission or thermal ionization of impurity centers.