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Notes: Recent studies [Hattangady et al., Appl. Phys. Lett. 57, 581 (1990)] have shown greatly reduced interface state densities (5×1010 cm−2 eV−1) in Ge-based, metal-insulator-semiconductor structures with the use of an ultrathin, pseudomorphic Si interlayer between the gate dielectric, SiO2, and the Ge semiconductor substrate. The Si and the SiO2 layers are deposited in situ and sequentially at low temperature (300 °C) in a remote-plasma-enhanced chemical-vapor-deposition system. This report presents an analysis of the Si-Ge heterostructure before and after the SiO2 deposition. Low-energy He ion scattering spectroscopy shows that the silicon layer (28 A(ring)) provides complete coverage of the Ge surface prior to the deposition of the SiO2 film. The existence of the silicon interlayer after the remote-plasma-enhanced deposition of 150 A(ring) of the SiO2 film is established by x-ray photoelectron spectroscopy (XPS). Throughout a cumulative series of thin (∼10 A(ring)) oxide depositions, XPS showed no evidence of Ge oxidation states other than Ge0+ (elemental Ge) at the interface. Quantitative XPS has been used to evaluate the extent of subcutaneous oxidation which could determine the amount of Si remaining at the interface and thereby influence the electrical properties of the semiconductor-oxide interface. For the conditions studied, it is observed that oxidation consumes only 4 A(ring) of the initial 28 A(ring) of silicon.Furthermore, this is apparently due to the plasma oxidation of the silicon at the initiation of the remote oxygen plasma discharge. Subcutaneous oxidation is limited thereafter by the oxide film that forms a barrier to oxygen diffusion. In addition, the XPS analysis reveals several important characteristics of SiO2-Si interface formation with these plasma-deposited SiO2 dielectric films. Inversion-mode, p-channel Ge field-effect transistors fabricated with this composite SiO2-Si gate dielectric structure show a maximum room-temperature transconductance of 52 mS mm−1 at a gate length of 2 μm and a peak effective channel hole mobility of 430 cm2 V−1 s−1. These devices exhibit negligible charge-induced threshold shifts.

Notes: In situ cleaning of GaAs surfaces has been achieved at 350 °C with a novel technique employing hydrogen that is excited and dissociated using a remote Ar discharge. Reconstructed surfaces characteristic of clean, As-stabilized GaAs surfaces have been observed with reflection high-energy electron diffraction following the cleaning treatment. Auger electron spectroscopy analyses confirm that such a treatment removes both carbon and oxygen contamination from the surface. X-ray photoelectron spectroscopy shows the removal of oxygen bonded to both Ga and As on the surface. Emission spectroscopy shows evidence of excited molecular and atomic hydrogen with the downstream-excitation process.

Notes: Significant improvements in gating of Ge surfaces are achieved with the use of thin, pseudomorphic Si interlayers. Metal-insulator-semiconductor structures with mid-gap interface state densities of 5×1010 cm−2 eV−1 and showing no hysteresis have been realized on both n- and p-type Ge. The key elements of this technology are: surface cleaning, deposition of a thin Si interlayer, and the deposition of the gate dielectric, SiO2, all of which are performed in situ and sequentially at 300 °C in a single chamber with the remote plasma technique. Ion scattering spectroscopy shows complete coverage of the Ge surface by the Si layer. X-ray photoelectron spectroscopy shows the Si interlayer is about 18 A(ring) thick. The Si interlayer prevents the interfacial oxidation of the underlying Ge.

Notes: The role of chemisorbed hydrogen in the enhancement of low-energy electron emission from natural type IIb C(001) diamond surfaces has been investigated. A hydrogen induced low-energy emission peak, whose intensity was found to be a linear function of surface coverage, was observed. The direct observation of emission from vacuum level states in the photoemission spectra has determined a negative electron affinity of ∼0.4 eV for the hydrogenated C(001)-1×1 surface. Constant initial states photoemission has unambiguously identified the electron emission process with the escape of electrons from bulk electron states at the conduction-band minimum. © 1997 American Institute of Physics.

Notes: Epitaxial Si films have been deposited on Si(100) at 300 °C by remote plasma-enhanced chemical vapor deposition using SiH4/H2 mixtures with deposition rates as high as 25 A(ring)/min at these low temperatures. Hall measurements of the film show an unintentional doping level of about 1×1017 cm−3 with electron mobilities of 700 cm2 V−1s−1. Critical to the process is the in situ cleaning of the silicon substrate surface prior to deposition.

Notes: Polished nominal (100) surfaces of four types of diamonds were exposed to atomic hydrogen by hot filament cracking of H2 gas or by immersion in a H2 plasma discharge. Both types IIa and IIb (100) diamond surfaces exhibited the following characteristic changes: (a) secondary electron (SE) yield increased by a factor of ∼30 as measured in a scanning electron microscope (SEM), (b) near-surface, nontopographical defects were observable directly using the conventional SE mode of the SEM, (c) surface conductance increased by up to 10 orders of magnitude. These changes were observed only weakly in nitrogen-containing types Ia and Ib diamonds.