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Notes: The depth distribution of sulphur near the Si/GaAs(110) interface has been measured using particle induced x-ray emission (PIXE) in conjunction with Rutherford backscattering spectrometry (RBS); ozone oxidation and a hydrofluoric acid step-etching technique were used for sequential removal of Si/GaAs atomic layers. The depth resolution was also calibrated via 16O(d,p)17O nuclear reaction analysis and x-ray photoemission spectroscopy. PIXE/RBS measurements found a half monolayer of sulphur on the H2Sx passivated GaAs(110) surface. Upon deposition of 15 A(ring) silicon on the S-passivated GaAs(110), the total amount of sulphur remained constant as compared to that before Si deposition. However, no orientated S–Ga bonds were detected via the x-ray absorption measurement and the depth profile revealed that the sulphur atoms diffused into both the GaAs substrate and the Si heterolayer. © 1996 American Institute of Physics.

Notes: Deep-level bulk and interface defect states in InP metal/insulator/semiconductor diodes have been investigated using capacitance-voltage measurements and deep-level transient spectroscopy. The InP surfaces were cleaned with an ultraviolet light/ozone/HF process followed by an optional polysulfide passivation and then capped with a layer of silicon nitride produced by remote plasma-enhanced chemical-vapor deposition. Polysulfide treatment reduced the bulk trap concentrations produced during contact annealing, reducing a bulk trap at 0.33 eV below the measurement limits and reducing a 0.45 eV trap to a concentration of 5×1013 cm−3. The density of interface states close to the conduction-band edge also decreased with the polysulfide treatment.

Notes: The quaternary III–V compound semiconductor GaInAsP is an important material for many optoelectronic devices, the surface of which generally needs to be passivated in the fabrication of such devices. Thus understanding the surface chemistry and monitoring the surface band gap states after oxidation and sulphur passivation have become necessary. Further, understanding the effect of ion bombardment on the GaInAsP surface during dielectric deposition is also of importance for device fabrication. In this study, quaternary GaInAsP(100) surfaces were subjected to UV/ozone and wet chemical treatments, dilute HF etching, sulfur passivation, and Ar ion bombardment. The composition and the relative movement of the surface Fermi level (EFs) of the surfaces were measured by x-ray photoemission spectroscopy (XPS) after oxidation, HF etching, sulfur passivation, and ion bombardment of surfaces. It was found that oxidation by ozone exposure formed multiple oxide phases of all the constituent elements. Both HF etching and sulfur passivation treatments were effective in generating surfaces having almost no oxide. It was also found that while sulfur passivation combined with an ultrahigh vacuum annealing at 300 °C reduced the surface band bending on n-type GaInAsP(100), it inverted p-type GaInAsP to n-type. An L-edge absorption spectrum of the sulfur passivated surface confirmed the presence of a sulfur layer. Further, it was found that an Ar+ ion bombardment pins the EFs near the midgap for both n- and p-type GaInAsP surfaces. © 1997 American Institute of Physics.

Notes: A new low-voltage contrast mechanism due to electron-hole pairs generated in the oxide by an electron beam was observed at electric fields lower than 3.5 MV/cm. This is in addition to the tunneling current microscopy (TCM) contrast mechanism observed at electric fields higher than 3.5 MV/cm. The new contrast mechanism is opposite in sign to the TCM contrast mechanism such that the image of a local thinning defect in the oxide is dark at low bias voltage and bright at higher bias voltage. Good contrast can be obtained at electric field as low as 2.4 MV/cm. Applications include large area imaging of oxide defects and quantitative mapping of small oxide thickness variations. © 1995 American Institute of Physics.

Notes: Diamondlike carbon films were deposited on germanium crystals with a mass-separated C+ ion beam in ultrahigh vacuum over the energy range 20–275 eV, and the interfaces were characterized with x-ray photoelectron spectroscopy. It was found that ion bombardment induced a carbide phase on the germanium surface. Further carbon accumulation then led to the growth of an amorphous carbon overlayer. The carbide phase was identified by a rather low C 1s binding energy (at about 283.8 eV) and small positive shift of the Ge 3p peak (about 0.4 eV). The valence-band spectra of these samples also suggested that germanium carbide formed with a pure carbon beam for the bombardment energy range considered has a band gap between germanium and diamondlike carbon.

Notes: The surface defect structures on diamond (100) surfaces induced by 500 eV neon ion bombardment and by subsequent annealing were studied in situ with x-ray absorption near-edge structure (XANES) spectroscopy using 250–800 eV synchrotron radiation and with low energy electron diffraction. Ex situ x-ray photoemission spectroscopy (XPS) was also used to characterize the defective layer. Significant changes in the XANES spectra were identified for the defects induced by ion bombardment and subsequent annealing. The diamond discrete exciton absorption at 289.0 eV was clearly suppressed even at the lowest ion fluence used in this study, i.e., 3×1014/cm2, and no such exciton could be observed at 7×1014/cm2. However, the changes in the multi-maxima shape-resonance absorption structure in the range of 290–310 eV indicated that a loss of the diamond long range order required a fluence of 1×1015/cm2. The structural changes were also manifested by the transformation of gap state absorption typical of clean 2×1 surfaces to the π* absorption typical of amorphous carbon. XPS showed that the defective layer was about 2 nm thick. For all samples prepared with the bombardment conditions in the study, both the XANES and XPS data also indicated no phase transformation from defective layers to graphite even after annealing to a temperature of 1100 °C. © 1994 American Institute of Physics.

Notes: Metal-insulator-semiconductor capacitors were fabricated on cleaved n-GaAs (110) facets using remote plasma-deposited silicon nitride as gate insulators. The interface properties of the capacitors made on this surface were analyzed by capacitance-voltage (C-V) measurements. X-ray photoemission spectroscopy was also used to investigate the chemical structure of the interface. Prior to the insulator deposition, the cleaved facets were processed with different surface treatments including HF etch of native oxide, passivation with an ammonium sulfide solution, passivation with hydrogen polysulfide, and passivation with a silicon interface control layer. It was found that while the passivation procedures with the sulfur compounds did improve the C-V data when compared with the HF oxide etch, the silicon interface control layer technique led to the best C-V results. By comparing the quasistatic and high-frequency (1 MHz) C-V data, it was found that the minimum interface state density of the fabricated capacitors was about 1012 eV−1 cm−2. © 1994 American Institute of Physics.

Notes: In the present study, a modified charge neutralizer was used to generate both the negative and positive surface potentials at the dielectric surface for the surface charge spectroscopy (SCS). A stable surface potential and a uniform potential area can be easily achieved. The SCS results of plasma enhanced chemical vapor deposition SiO2/Si samples without annealing and thermal SiO2/Si samples with and without annealing in forming gas (4%H2 in N2) are used to demonstrate the applicability of the SCS analysis. © 1995 American Institute of Physics.

Notes: A defect state, defect B, was found in Ta2O5 after postdeposition annealing in O2 by a novel zero-bias thermally stimulated current spectroscopy technique. The activation energy ET was estimated to be about 0.3 eV. Evidence is given that defect B is a hole trap. We believe that defect B is an acceptor level in Ta2O5 due to Si substituting for Ta. The presence of Si contamination in Ta2O5 due to diffusion of Si from the Si substrate into Ta2O5 was confirmed by secondary-ion-mass spectrometry. © 1996 American Institute of Physics.

Notes: Argon and carbon ion bombardment of p-diamond at 500–5000 eV in ultrahigh vacuum were studied by in situ x-ray photoelectron spectroscopy (XPS) and low energy electron diffraction analysis. Both argon and carbon ion bombardment at room temperature in the present energy range created a defective surface layer. The radiation damage was manifested by the introduction of a distinct C 1s peak (referred to as the "defect'' peak later) with a binding energy about 1 eV less than that of the bulklike diamond peak, and by the introduction of some additional filled states (referred to as the "filled states'') near the valence band edge of diamond. It was found that in comparison to argon bombardment, carbon bombardment was more efficient in producing the filled states but less efficient in raising the C 1s defect peak. While the filled states disappeared by annealing at about 500 °C, the C 1s defect peak did not change much even with a 1000 °C anneal. These results suggest that the C 1s defect peak, which has also been observed on reconstructed diamond surfaces after hydrogen desorption [see, e.g., B. B. Pate, Surf. Sci. 165, 83(1986)], is associated with vacancy formation and aggregation which give some "internal surfaces'' with a behavior like a reconstructed atomically clean diamond surface.The filled states introduced by ion bombardment are associated with interstitials or interstitial clusters. The amount of residual defects was found to increase with both an increasing bombardment dose and energy. For an argon bombardment at 1000 eV to a dose of 5×1014/cm2, the defective layer was estimated to be about 1.5 nm. Further, it was found that the radiation damage, particularly the "vacancy defects'', could only be annealed (at 1000 °C) when the dose was below 5×1014/cm2 at a bombardment energy of 500 eV. XPS band bending analyses also showed that room temperature bombardment induced a small reduction (0.2 eV) of the surface Fermi level position (EFs) on the p-diamond. However, subsequent vacuum annealing caused a rather large increase of EFs. But the EFs data from about 20 bombarded and annealed samples were always less than 2.2 eV. Thus the formation of an n-type diamond was not observed.