Semiconductor Surface Passivation Research Articles

Multipole moment description of passivants and complex pseudopotentials for semiconductor surfaces

From a theoretical point of view, surface passivation of semiconductors can be handled with the inclusion of hydrogen-like complex pseudopotentials. In this work, we show that the two components of such potentials are not spherical and that they correspond to different multipole electric moments of the passivant atom. In particular, we find that the real part of the complex pseudopotential behaves like a quadrupole and has an angular dependence. We show that disregarding the multipole description may lead to the occurrence of surface-localized virtual states between the conduction and valence bands. The multipole moments are identified according to their dependence upon the distance in real space. The effectiveness of our complex-pseudopotential passivation is demonstrated by calculating the band-gap energy of quantum wires and quantum slabs along different orientations for different materials (GaAs, AlAs, CdSe, Ge, and Si). Our derivation constitutes an improvement to the pseudopotential method and a more physically accurate description of passivants, whose real component has been treated as a spherically symmetric quantity.

POx/Al2O3 stacks for surface passivation of Si and InP

Passivation of semiconductor surfaces is crucial to reduce carrier recombination losses and thereby enhance the device performance of solar cells and other semiconductor devices. Thin-film stacks of phosphorus oxide (PO x ) and aluminum oxide (Al 2 O 3 ) have recently been shown to provide excellent passivation of semiconductor surfaces, including crystalline silicon and indium phosphide, and can also be highly interesting for passivation of other semiconductor materials such as Ge and III-V semiconductors. On silicon, the excellent passivation is attributed to the combination of a high positive fixed charge and a very low interface defect density. On InP nanowires, application of the PO x /Al 2 O 3 stacks improves charge carrier lifetime threefold as compared to unpassivated nanowires. In this work, we review and summarize recent results obtained on PO x /Al 2 O 3 stacks for semiconductor surface passivation. Several topics are discussed, including the passivation performance on various semiconductor surfaces, the processing of the PO x and Al 2 O 3 layers, the role of the capping layer, and aspects related to device integration. The PO x /Al 2 O 3 stacks feature some unique properties, including an unusually high positive fixed charge density, a low interface defect density, and can be prepared over a wide deposition temperature range. These unique properties arise in part from the mixing process that occurs between the PO x and Al 2 O 3 layers, which upon post-deposition annealing leads to the formation of AlPO 4 . The surface passivation provided by PO x /Al 2 O 3 stacks is highly stable and the stack can be used to conformally coat high-aspect-ratio structures such as nanowires, showing their promise for use in semiconductor devices. • PO x /Al 2 O 3 stacks provide excellent surface passivation on Si and InP. • PO x /Al 2 O 3 has a unique high positive fixed charge density (10 12 -10 13 cm −2 ) on Si. • PO x /Al 2 O 3 has low interface defect density down to 10 10 -10 11 eV −1 cm −2 on Si. • The Al 2 O 3 layer mixes with PO x during deposition, leading to AlPO 4 upon annealing. • The surface passivation quality provided by PO x /Al 2 O 3 is stable for over 1000 days.

Study of electrical properties of Al/Si3N4/n-GaAs MIS capacitors deposited at low and high frequency PECVD

As for silicon, surface passivation of GaAs and III-V semiconductors using silicon nitride (Si3N4) deposited by plasma enhanced chemical deposition (PECVD) is widely used to improve devices and circuits stability, reliability and for encapsulation. In this work, the effect of plasma excitation frequency in the PECVD reactor on the surface passivation efficiency of GaAs during Si3N4 deposition was investigated. Metal-Insulator-Semiconductor (Al/Si3N4/n-GaAs) capacitors are fabricated and characterized using capacitance–voltage (C–V), and conductance–voltage (G–V) to compare electronic properties of GaAs/Si3N4 interfaces depending on the use of a high frequency PECVD (HF-PECVD) or low frequency (LF-PECVD) process. The drastic advantage of using the LF-PECVD technique for the passivation of GaAs is clearly demonstrated on the characteristic C–V at 1 MHz where a good surface potential was observed, while a quasi-pinned surface Fermi level was found when HF-PECVD was used. To unpin Fermi level, a sulfur pre-treatment prior before HF-PECVD deposition and post-metallisation annealing were necessary. A lower frequency dispersion and a lower hysteresis indicating low densities of slow traps were observed for MIS devices fabricated by LF-PECVD. The advantage of having an efficient passivation without sulfur treatment is important since ammonium sulfide used for this purpose is corrosive and difficult to adapt in industrial environment. The better electronic properties of GaAs/Si3N4 interface were found for silicon nitride layers using LF-PECVD deposition. This can probably be associated with the high-level injection of H+ ions on the semiconductor surface reducing thus the native oxides during the initial steps of dielectric deposition.

(Invited) Semiconductor Surface Passivation by ALD and CVD Prepared Nanolayers

For (opto)electronic devices, it is generally key to reduce the trapping and recombination of charge carriers at the semiconductor surfaces and interfaces. This is becoming more and more challenging due to the ongoing diversification in semiconductor materials to be used in the devices (extending from Si to (Si)Ge and from group-IV to group-III-V semiconductors) but also due to the increasing surface-to-volume ratio of the nanostructures employed. Surface passivation can be achieved by employing thin films of semiconductor or dielectric materials which often serve other functionalities in the devices too. The underlying mechanism of the surface passivation can be the reduction of surface defect states (i.e. so-called chemical passivation) and/or band bending due to so-called field-effect passivation effect (e.g. due to fixed charges in the film).In this contribution the surface passivation of semiconductors by recent innovative nanolayer approaches will be presented. These nanolayers include materials such as Al2O3, POx, a-Si:H and (doped) ZnO as well as stacks thereof. The preparation of the materials by (plasma-enhanced) chemical vapor deposition (CVD) and atomic layer deposition (ALD) will be discussed as well as the application of the nanolayers on semiconductors such as Si, SiGe, Ge and InP. Results will be presented for both wafers and nanowires. Special attention will be given to the underlying mechanism of the surface passivation achieved as well as its relation to the properties of the nanolayers employed. Figure 1

Interface Engineering for High‐Performance Photoelectrochemical Cells via Atomic Layer Deposition Technique

Photoelectrochemical (PEC) water splitting is renowned as artificial photosynthesis. It is considered as a promising candidate for sustainable solar energy conversion and chemical production. For decades, great efforts have been made to develop PEC cells with low costs, high conversion efficiencies, and high stabilities. Surface and interface engineering has been proven to be of two key parameters to the performance of PEC cells, especially for hybrid structures. Among the many interface engineering preparation technologies, atomic layer deposition (ALD) technology has occupied the research hotspots of these decades due to its unique advantages. Its self‐limiting reaction mechanism, perfect conformality, and atomic‐level control of thickness and composition bring many new possibilities to surface and interface engineering of PEC cells. Herein, the interface engineering of PEC water splitting by ALD is mainly introduced. The comprehensive performance of PEC cells’ interface engineering, including electrode surface protection based on ALD technology, semiconductor surface passivation, heterojunction interface band alignment engineering, catalyst/semiconductor interface modification, etc. is introduced. At the same time, the future development trends and challenges of PEC cell interface engineering based on ALD technology are also discussed.

Reaction of Hydrazine with Solution- and Vacuum-Prepared Selectively Terminated Si(100) Surfaces: Pathways to the Formation of Direct Si-N Bonds.

The reactivity of liquid hydrazine (N2H4) with respect to H-, Cl-, and Br-terminated Si(100) surfaces was investigated to uncover the principles of nitrogen incorporation into the interface. This process has important implications in a wide variety of applications, including semiconductor surface passivation and functionalization, nitride growth, and many others. The use of hydrazine as a precursor allows for reactions that exclude carbon and oxygen, the primary sources of contamination in processing. In this work, the reactivity of N2H4 with H- and Cl-terminated surfaces prepared by traditional solvent-based methods and with a Br-terminated Si(100) prepared in ultrahigh vacuum was compared. The reactions were studied with X-ray photoelectron spectroscopy, atomic force microscopy, and scanning tunneling microscopy, and the observations were supported by computational investigations. The H-terminated surface led to the highest level of nitrogen incorporation; however, the process proceeds with increasing surface roughness, suggesting possible etching or replacement reactions. In the case of Cl-terminated (predominantly dichloride) and Br-terminated (monobromide) surfaces, the amount of nitrogen incorporation on both surfaces after the reaction with hydrazine was very similar despite the differences in preparation, initial structure, and chemical composition. Density functional theory was used to propose the possible surface structures and to analyze surface reactivity.

Anomalous minority carrier behavior induced by chemical surface passivation solution in p-type GaSb metal–oxide–semiconductor capacitors on Si substrates

p-type GaSb metal–oxide–semiconductor capacitors with thin InAs surface capping layers were prepared on Si(001) substrates. Epitaxial structures with superlattice metamorphic buffer layers were grown by molecular beam epitaxy. Chemical surface treatment and atomic layer deposition methods were employed for a semiconductor surface passivation and Al2O3 high-k oxide fabrication, respectively. Capacitance-voltage measurements and scanning and transmission electron microscopies were used to correlate electrical properties with the oxide-semiconductor interface structure of the capacitors. Unexpectedly, fast minority carrier response present down to liquid nitrogen temperature was observed in the capacitors passivated by an ammonium sulfide solution. This fast response was found to be related to etch pitlike surface morphology developed upon chemical passivation at the surface steps formed by microtwins and antiphase domain boundaries. Preferential InAs etching by ammonium sulfide at the surface defects was confirmed by analytical TEM studies. Very low activation energy of minority carrier response suggests the presence of electron sources under the gate; they result from growth-related surface defects that give rise to potential fluctuations of as high as half the GaSb bandgap.

Defects Near c-Si(n++)/TiO2 Interfaces Revealed By Persistent Charging Analysis in Modulated Surface Photovoltage Spectroscopy

Thin layers of semiconductors with wide band gaps (wide gap SCs), such as TiO2, are of great interest for the passivation and/or specific activation of semiconductor surfaces in photoelectrochemical (PEC) systems [1]. Defect states in the bulk of wide gap SCs and at related semiconductor hetero-junctions play an important role for the electronic properties of PEC systems. Due to high activation energies in wide gap SCs, electronic states can be charged for relatively long times. This persistent charging of wide gap SCs can have large impact on photogeneration and modulated charge separation in modulated surface photovoltage (SPV) spectroscopy and thus opens a new perspective for the investigation of electronic defect states at/near interfaces with wide gap SCs. In this work, persistent charging is applied to the investigation of defect states in c-Si(n++)/TiO2(ALD) systems before and after conversion from amorphous TiO2 to anatase by post annealing.Thin layers of amorphous TiO2 with thicknesses of up to 100nm were deposited onto highly doped silicon wafers (c-Si(n++)) and converted into anatase by annealing for 30 min at 450°C. Modulated SPV measurements were performed at room temperature in the fixed capacitor arrangement [2] with a quartz prism monochromator and a xenon arc lamp for excitation over a range from 0.8 to 4.5 eV. Incidentally, the in-phase (X) or phase-shifted by 90° (Y) signals are much faster or slower, respectively, than the modulation period (see for details also [3]).The X- and Y- signals of two modulated SPV spectra were measured subsequently within about 30 min. This kind of measurement regime opened the opportunity for the analysis of the influence of charging on electronic transitions of defect states in c-Si(n++)/TiO2(ALD) systems and it will be straight forward to compare those results with the optical properties of holes and electrons trapped in TiO2 [4].As an example, the figure shows modulated SPV spectra of an as prepared (a) and annealed (b) sample. The X-signals of the as-prepared sample where quenched with ongoing absorption in amorphous TiO2 whereas the onset energy for quenching shifted by more than 0.1 eV towards lower energies for the second scan. In contrast, the Y-signals of the as-prepared sample became more negative between about 3 and 3.5 eV and changed to more positive and changed sign at higher photon energies. Electrons photogenerated in amorphous TiO2 near the interface with c-Si were transferred into c-Si and partially trapped near the interface resulting in an increase of the SPV signals related to photogeneration in c-Si(n++) and in quenching of charge transfer from amorphous TiO2 into c-Si(n++) in the second scan.For the annealed sample, the signals were much larger and modulated charge separation with opposite direction at the c-Si and TiO2 surfaces became dominant. The Y-signals for the virgin scan were larger than for the second scan at photon energies up to about 2.5 eV, but smaller for higher photon energies, i.e. photogeneration by defects in anatase caused an increase of positive charge at the interface with c-Si(n++) and of negative charge at the external surface whereas the signature of the hole traps nearly disappeared in the second scan shown in the figure.Furthermore, the influence of the specific spectrum of the photon flux could be widely eliminated by analyzing the spectra of the ratio of the amplitudes before and after charging (not shown) which allowed for the extraction of defect peaks induced by charging.Acknowledgement: The authors are grateful to A. Schwartzberg, D. Olynick and S. Cabrini for their insight and support for the preparation and coating of the samples by atomic layer deposition. The authors furthermore gratefully acknowledge financial support by the Federal Ministry of Education and Research of Germany, in the framework of the project "FocusH2" (No. 03SF0479A). The transient SPV spectroscopy instrumentation was developed at HZG with support from the Helmholtz Association of German Research Centres, within the "HEMF" platform (Helmholtz Energy Materials Foundry). Work at the Molecular Foundry was supported by the Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.[1] S. Hu et al., Science 344 (2014) 1005.[2] V. Duzhko et al., Phys. Rev. B 64 (2001) 075204.[3] Th. Dittrich, S. Fengler, Surface photovoltage analysis of photoactive materials, World Scientific. ISBN No. 978-1786347657 (2019).[4] D. Bahnemann et al., J. Phys. Chem. 88 (1984) 709; Bahnemann et al., J. Phys. Chem. B 101 (1997) 4265; R. Memming, Semiconductor Electrochemistry, Wiley-VCH (2001 2nd ed. 2015); J. Schneider and D. Bahnemann, J. Phys. Chem. C 122 (2018) 13979. Figure 1

Passivation of the CuInSe2 surface via cadmium pre-electrolyte treatment

Effective defect passivation of semiconductor surfaces and interfaces is indispensable for the development of high efficiency solar cells. In this study we systematically investigated the surface and grain boundary properties of ${\mathrm{CuInSe}}_{2}$ (CISe) with scanning tunneling microscopy (STM) and spectroscopy (STS) after different surface treatments such as potassium cyanide (KCN) etching, pre-electrolyte treatment with cadmium ions, and annealing in ultrahigh vacuum (UHV). We show that air exposed samples with a subsequent KCN etching step exhibits a highly defective surface. However, a Cd pre-electrolyte treatment passivates most of these defects, which manifests itself by a reduction of the high conductance in the STS measurements at positive sample biases. The origin of the improvement can be traced back to an increase in surface band bending, which leads to a type inversion, induced by a change in the concentration of Cu vacancies. We observe a defect passivation at the CISe surface and at the grain boundaries. Our results give a direct explanation of why the CdS buffer layer in CISe thin film solar cells is of utmost importance for high efficiency devices.

Synthesis and structural characterization of microcrystalline Ga2S3 layers on a GaP semiconductor substrate

Gallium sulfide (Ga2S3) belongs to a group of wide bandgap semiconductors with interesting properties for infrared and nonlinear optics applications. Recent interest in Ga2S3 material focuses on the passivation of various semiconductor surfaces to enhance their electrical and optical properties. This work concerns the growth of microcrystalline gallium sulfide layers on semiconductive GaP substrates. The Ga2S3 layers were successfully obtained by reacting sulfur vapour with thin GaP semiconductor plates at two different temperatures: 450 °C and 600 °C. At the lower temperature (400 °C), no gallium sulfide layer formation was observed on the GaP substrate. Atomic force microscopy and Scanning Electron Microscopy were applied to illustrate the topography of the obtained Ga2S3 layers. Their thickness ranged from a few hundred nanometers to about 1–2 µm. The synthesized layers were structurally characterized by Raman spectroscopy. Raman polarization measurements were used to determine the crystalline phase of the Ga2S3 films. Raman tensor coefficients were obtained by fitting the most intensive Ga2S3 peaks to experimental data. The symmetry of the Raman peaks was in good agreement with the monoclinic Ga2S3 crystal phase.

Surface passivation of InP using an organic thin film

We demonstrate the surface passivation of InP using thin layers of a perylenetetracarboxylic diimide derivative (PTCDI-C9) applied via organic vapor phase deposition (OVPD). The organic layer forms a conformal crystalline film on the InP surface, which is confirmed by atomic force microscopy and X-ray diffraction. Area-dependent photoluminescence measurements indicate that the coating reduces surface recombination. The organic thin film deposited by OVPD exhibits improved photoconductivity compared to an unpassivated InP sample, and to a layer deposited via vacuum thermal evaporation. Our results suggest that semiconductor surface passivation using organic thin films deposited by OVPD has applications to a variety of optoelectronic devices, particularly with structures requiring sidewall or conformal coatings.

Functional Organophosphonate Interfaces for Nanotechnology: AReview.

Optimization of interfaces in inorganic-organic device systems depends strongly on understanding both the molecular processes that are involved in surface modification and the effects that such modifications have on the electronic states of the material. In particular, the last several years have seen passivation and functionalization of semiconductor surfaces to be strategies by which to realize devices with superior function by controlling Fermi level energies, band-gap magnitudes, and work functions of semiconducting substrates. Among all of the synthetic routes and deposition methods available for the optimization of functional interfaces in hybrid systems, organophosphonate chemistry has been found to be a powerful tool to control at the molecular level the properties of materials in many different applications. In this Review, we focus on the relevance of organophosphonate chemistry in nanotechnology, giving an overview about some recent advances in surface modification, interface engineering, nanostructure optimization, and biointegration.

(Invited) Surfactant-Assisted Chemical Vapor Deposition of High-Performance Small-Diameter Gasb Nanowires

Due to the intriguing physical properties, III-Sb nanowires such as GaSb have attracted extensive interest as promising channel materials for future electronics, optoelectronics and others. Although various device structures based on GaSb nanowires have been realized, further performance enhancement is still suffering from the notorious uncontrolled radial growth during the nanowire synthesis, resulting in the non-uniform and tapered nanowires with diameters much larger than few tens of nanometers. In this work, for the first time, we report the use of sulfur surfactant in the chemical vapor deposition to achieve high-performance and uniform GaSb nanowires with the diameter down to 20 nm. In contrast to the surfactant effect typically employed in the liquid phase or thin film technologies, the sulfur atoms, commonly used for the surface passivation of III-V semiconductors, are contributed to form stable S-Sb bonds on the as-grown nanowire surface, effectively stabilizing the sidewalls and thus minimizing the unintentional radial vapor-solid nanowire growth. More importantly, when configured into field-effect transistors, these nanowire devices exhibit impressive electrical properties with the peak field-effect hole mobility of ~200 cm2 V-1 s-1, which is the best mobility value reported for any GaSb nanowire devices till now, owing to the improved gate-coupling efficiency and reduced surface carrier scattering in these thin nanowire geometry. All these results evidently indicate the effectiveness of this surfactant-assisted growth for high-performance small-diameter GaSb nanowires, significantly enhancing various device properties for practical applications.

The effect of passivation on different GaAs surfaces

The surface passivation of semiconductors on different surface orientations results in vastly disparate effects. Experiments of GaAs/poly(3,4-ethylenedioxythiophene/indium tin oxide solar cells show that sulfur passivation results in threefold conversion efficiency improvements for the GaAs (100) surface. In contrast, no improvements are observed after passivation of the GaAs (111B) surface, which achieves 4% conversion efficiency. This is explained by density-functional theory calculations, which find a surprisingly stable (100) surface reconstruction with As defects that contains midgap surface states. Band structure calculations with hybrid functionals of the defect surface show a surface state on the undimerized As atoms and its disappearance after passivation.

Liquid-Phase Adsorption of Sulfur on Germanium: Reaction Mechanism and Atomic Geometry

We present a fundamental study of the monolayer adsorption of sulfur on Ge(100) surfaces from aqueous (NH4)2S solution. This treatment shows promising perspectives for the passivation of high-mobility semiconductor surfaces and is therefore presently of great technological importance. The adsorption mechanisms as well as the adsorption geometry are thoroughly investigated at the atomic scale, by both experiment and theory, applying X-ray absorption spectroscopy and molecular dynamics simulations. Our findings indicate that sulfidation in solution results in the formation of Ge–S–Ge bridges along the [110] direction, with no indication for −SH surface groups. A S–Ge bond length of 2.25 ± 0.05 A was deduced, which is affected by the chemical environment of the sulfur atoms, i.e., by residual surface oxides. Our study provides novel insights into the surface termination and atomic structure of (NH4)2S-treated Ge(100) surfaces and discusses possible differences from in situ sulfur adsorption methods such as H...

Theoretical analysis of semiconductor surface passivation by adsorption of alkaline-earth metals and chalcogens

We begin with the concept of semiconductor surface passivation by adsorption of sub-monolayer atomic coverages. We then present a theoretical analysis of structural reconstruction and passivating behaviour of semiconductor surfaces upon sub-monolayer adsorption of alkaline-earth metals (group II atoms) and chalcogens (group VI atoms). Specific results are presented from first-principles calculations for Ca adsorption on Si(001) and Si(111), and S adsorption on GaAs(001). The role of chemical species of adsorbate and surface atoms in achieving different degrees of passivation is highlighted.

Characterization of Semiconductor Surfaces during Surface Conditioning and Functionalization

Semiconductor surface cleaning, passivation and functionalization are critical steps for applications such as microelectronics, MEMS, sensors, and solar energy harvesting. Progress has relied in part on the development of surface chemical treatments. However, the ability to characterize surfaces at all steps of processing has also been essential and will be emphasized here. This work focuses on the chemical modification of oxide-free, hydrogen-passivated silicon, including wet chemical treatments, atomic layer deposition, and physical deposition. Characterization methods include in-situ infrared absorption spectroscopy, low energy ion scattering, x-ray photoelectron spectroscopy and mass spectrometry, and is complemented by ex-situ spectroscopic ellipsometry and atomic force microscopy.

Nitrogen interaction with hydrogen-terminated silicon surfaces at the atomic scale

Passivation of semiconductor surfaces is conveniently realized by terminating surface dangling bonds with a monovalent atom such as hydrogen using a simple wet chemical process (for example, HF treatment for silicon). However, the real potential of surface chemical passivation lies in the ability to replace surface hydrogen by multivalent atoms to form surfaces with tailored properties. Although some progress has been made to attach organic layers on top of H-terminated surfaces, it has been more challenging to understand and control the incorporation of multivalent atoms, such as oxygen and nitrogen, within the top surface layer of H-terminated surfaces. The difficulty arises partly because such processes are dominated by defect sites. Here, we report mechanistic pathways involved in the nitridation of H-terminated silicon surfaces using ammonia vapour. Surface infrared spectroscopy and first-principles calculations clearly show that the initial interaction is dominated by the details of the surface morphology (defect structure) and that NH and NH(2) are precursors to N insertion into Si-Si bonds. For the dihydride-stepped Si(111) surface, a unique reaction pathway is identified leading to selective silazane step-edge formation at the lowest reaction temperatures.

Passivation at semiconductor/electrolyte interface: Role of adsorbate solvation and reactivity in surface atomic and electronic structure modification of III–V semiconductor

These studies are focused on understanding the role played by a solvent in chemical and electronic processes occurred in the course of semiconductor surface passivation at semiconductor/electrolyte interface. It is shown that the chemical reactivity of the ionic adsorbate at a semiconductor/electrolyte interface can be changed considerably through interaction with solvent molecules. The reactivity of anions depends essentially on the solvating solvent: hydrated ions could be either slightly electrophilic or slightly nucleophilic, whereas the ions solvated by alcohol molecules are always strongly nucleophilic. Mechanism of interaction of such solvated ions with the semiconductor surface atoms depends on the solvent, as is demonstrated by the example of processes occurred at GaAs(1 0 0)/sulfide solution interfaces. It is found that on adsorption of HS − ions from different solvents the As S bonds with solvent-dependent ionic character are formed on a GaAs(1 0 0) surface. The surface obtained in such a way possesses different ionization energy and exhibit different electronic properties dependent on the solvent.

Passivation of Semiconductor Surfaces for Improved Radiation Detectors: X-Ray Photoemission Analysis

AbstractSurface passivation of device-grade radiation detector materials was investigated using x-ray photoelectron spectroscopy in combination with transport property measurements before and after various chemical treatments. Specifically Br-MeOH (2% Br), KOH with NH4F/H2O2 and NH4OH solutions were used to etch, reduce and oxidize the surface of Cd(1-x)ZnxTe semiconductor crystals. Scanning electron microscopy was used to evaluate the resultant microscopic surface morphology. Angle-resolved high-resolution photoemission measurements on the valence band electronic structure and core lines were used to evaluate the surface chemistry of the chemically treated surfaces. Metal overlayers were then deposited on these chemically treated surfaces and the I-V characteristics measured. The measurements were correlated to understand the effect of interface chemistry on the electronic structure at these interfaces with the goal of optimizing the Schottky barrier height for improved radiation detector devices.