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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: 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: 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: 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.

Notes: Argon incorporation in Si(100) by low energy ion bombardment has been studied by polar angle dependent x-ray photoelectron spectroscopy and Rutherford backscattering spectroscopy. The bombardment was performed at 15, 20, and 100 eV in an ultrahigh vacuum chamber where a mass-separated argon ion beam with an energy spread of less than 1 eV was directed to the target. Both the argon penetration depth and incorporation probability were found to increase with bombardment energy. With a fluence of 2×1017/cm2, most of the incorporated argon was located within 20 A(ring) of the target surface for the 100 eV bombardment and within 10 A(ring) for the 15 eV bombardment. In all cases, the argon depth distribution reached a maximum and then declined. At this fluence, the incorporation probabilities were 0.0015 and 0.0004 for the 100 and 15 eV bombardment, respectively. When the amount of incorporated argon was measured as a function of fluence, it increased with fluence at low fluences, reached a quasisaturation at about 1×1016/cm2, but became fluence dependent again above 1×1018/cm2. The retained argon was stable at room temperature but showed at least two stages of thermal desorption in the temperature range 25–500 °C.

Notes: Direct ion beam deposition of carbon films on silicon in the ion energy range of 15–500 eV and temperature range of 25–800 °C has been studied. The work was carried out using mass-separated C+ and CH+3 ions under ultrahigh vacuum. The films were characterized with x-ray photoelectron spectroscopy, Raman spectroscopy, transmission electron microscopy, and transmission electron diffraction analysis. In the initial stage of the deposition, carbon implanted into silicon induced the formation of silicon carbide, even at room temperature. Further carbon ion bombardment then led to the formation of a carbon film. The film properties were sensitive to the deposition temperature but not to the ion energy. Films deposited at room temperature consisted mainly of amorphous carbon. Deposition at a higher temperature, or post-deposition annealing, led to the formation of microcrystalline graphite. A deposition temperature above 800 °C favored the formation of microcrystalline graphite with a preferred orientation in the (0001) direction. No evidence of diamond formation in these films was observed.

Notes: An experimental study of the growth of fractal patterns during ion beam-solid interaction in the Ni-Zr alloy system is reported. The observed fractal patterns in the alloy films feature both isotropic and anisotropic characters depending on their growth surroundings. The fractal dimension of the isotropic fractal patterns is determined to be 1.4±0.1. The possible growth mechanism of the observed patterns is discussed.

Notes: Spontaneous vitrification was observed in the equilibrium immiscible Fe-Cu system. The metastable phase before vitrification was an icosahedral incommensurate phase which was formed by an ion beam mixing of Fe-Cu multilayer films at room temperature and subsequent high-temperature thermal annealing. The electrical and magnetic properties of the icosahedral phase are also reported, and the relation with spontaneous vitrification is discussed.