Effect Of Hydrogen Termination Research Articles

Effects of hydrogen termination of CVD diamond layers

This paper is focused on studies of hydrogen terminated diamond films deposited from CH3OH and H2 gas mixture.The polycrystalline diamond layers of different ratios of sp2/sp3 carbon phases and levels of H-termination were synthesized by Hot Filament Chemical Vapour Deposition (HF CVD) method. As-grown CVD diamond layers were naturally hydrogen terminated which results from the nature of the CVD growth process.It is well known that hydrogen is responsible for the hydrophobic properties of the diamond surface and for its p-type conductivity, however, knowledge about the influence of hydrogen on optically active centers is very limited.The performed photoluminescence studies have shown that chemically bonded hydrogen can passivate non-radiative defects making the radiative transition more probable.In present work the properties of diamond surface has been studied using SEM (morphology), X-ray Powder Diffraction (XRD), Raman and photoluminescence spectroscopies (structural quality, carbon phases composition, photoluminescence properties), FTIR spectroscopy (confirmation of H-termination), PL (photoluminescence), X-ray photoelectron spectroscopy (XPS) and contact angle (wetting properties-hydrogen termination).

Hydrogen-terminated detonation nanodiamond: Impedance spectroscopy and thermal stability studies

In this paper, we investigated the effect of hydrogen termination on the electrical properties and impedance spectra of detonation nanodiamond. The impedance spectra revealed that the hydrogen-termination process increases the electrical conductivity by four orders of magnitude at room temperature. An equivalent circuit has been proposed to correlate with the conduction mechanism. Arrhenius plot showed that there were two different activation energy levels located at 0.089 eV and 0.63 eV between 50 °C and 400 °C. The possible physical mechanism corresponding to these activation energy levels has been discussed. Hydrogen-terminated detonation nanodiamond has been further annealed at different temperatures prior to FTIR and XPS measurements in order to understand their thermal stability. The results demonstrated that the surface oxidization occurred between 100 °C and 150 °C. However, the C–H bonds could partially survive when the temperature reaches 400 °C in air.

A Q-DLTS investigation of aluminum nitride surface termination

Abstract

Effect of Hydrogen Termination on Surface Roughness Variation of Si(110) by Reflow Oxidation during High-Temperature Ar Annealing

It is well known that a smooth surface can be realized for silicon (Si) wafers by Si surface reconstruction using high-temperature annealing. We previously reported that it is crucial to maintain a smooth reconstructed surface to restrict accidental oxidation during the unloading process (i.e., reflow oxidation) in high-temperature annealing. The surface roughnesses of both Si(100) and Si(110) were proved by suppressing the reflow oxidation. Furthermore, for suppressing the reflow oxidation, we evaluated the thickness of the reflow oxidation layer and the surface structure of the Si(110) wafer by replacing the injected Ar gas with H2 in the cooling process during high-temperature Ar annealing. The H2 atmosphere condition induced a change by etching the reconstructed surface, and the H-terminated surface on Si(110) formed SiH2, which effectively suppressed the reflow and characteristic line oxidations, resulting in a smooth terrace-and-step structure.

Thermal conductivity of graphene ribbons from equilibrium molecular dynamics: Effect of ribbon width, edge roughness, and hydrogen termination

We use equilibrium molecular dynamic simulations to compute thermal conductivity of graphene nanoribbons with smooth and rough edges. We also study effects of hydrogen termination. We find that conductivity is the highest for smooth edges and is essentially the same for zigzag and armchair edges. In the case of rough edges, the thermal conductivity is a strong function of the ribbon width indicating the important effect of phonon scattering from the edge. Hydrogen termination also reduces conductivity by a significant amount.

Palladium Thin-Films on Clean and Hydrogen-Terminated Si(110): The Effect of Hydrogen Termination on Metal Adsorption

A combined scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS), and low energy electron diffraction (LEED) study of the room-temperature deposition of palladium on wet-chemically-prepared H/Si(110) and vacuum-prepared Si(110) “16×2” was carried out to gauge the ability of a hydrogen barrier layer to restrict reactive adsorption of Pd on Si(110) (e.g. silicide formation) and to determine the effect of the hydrogen barrier layer on the growth mode of the deposited films. For deposition quantities less than 1.5 monolayers (ML), Pd atoms adsorbed in a random fashion on the clean Si(110) surface, while islands formed on the H/Si(110) surface. However, after ∼3 ML of deposition the film morphology took on a disordered hillock motif for both clean and hydrogen-terminated substrates. The size distribution of the hillocks was remarkably narrow, and indistinguishable for clean and hydrogen terminated substrates. Further, the hillock morphology was invariant with Pd deposition between 3 and ∼8 ML. XPS analysis revealed the deposited films to be chemically similar to Pd2Si for both Si(110) “16×2”, and H/Si(110) substrates, indicating that the hydrogen barrier layer does not prevent silicide formation.

Thermodynamical and plasma-driven kinetic growth of high-aspect-ratio nanostructures: effect of hydrogen termination

The results of studies on the growth of high-aspect nanostructures in low-temperature non-equilibrium plasmas of reactive gas mixtures with or without hydrogen are presented. The results suggest that the hydrogen in the reactive plasma strongly affects the length of the nanostructures. This phenomenon is explained in terms of selective hydrogen passivation of the lateral and top surfaces of the surface-supported nanostructures. The theoretical model describes the effect of the atomic hydrogen passivation on the nanostructure shape and predicts the critical hydrogen coverage of the lateral surfaces necessary to achieve the nanostructure growth with the pre-determined shape. Our results demonstrate that the use of a strongly non-equilibrium plasma is very effective in significantly improving the shape control of quasi-one-dimensional single-crystalline nanostructures.

Characterization of local electrical properties of polycrystalline silicon thin films and hydrogen termination effect by conductive atomic force microscopy

We observed local electrical properties of polycrystalline silicon films by conductive atomic force microscopy. Moreover, we investigated the effects of hydrogen termination on the polycrystalline silicon films. Before hydrogen termination, conductive regions in grain disappeared with the repeated scanning of the cantilever, while conductive regions in grain boundary almost unchanged. It is considered that hopping conduction is a major electrical conduction mechanism at grain boundaries. After 5 min hydrogen termination, locally nonterminated regions were observed near grain boundaries. This suggests that hydrogen termination of the polycrystalline silicon does not randomly progress, and there are regions that cannot be easily inactivated near grain boundaries.

Effect of Hydrogen Termination on Ba Reaction on the Si(100) Surface

The effect of hydrogen termination on Ba reaction on the Si(100) surface at the initial stage of Ba adsorption was investigated by means of scanning tunneling microscopy (STM). On the bare Si(100) surface, Ba atoms form chain-shaped structures of Ba coverage up to 1/3 monolayer (ML), which extend perpendicular to the Si dimer row. The chain-shaped structure can change its shape because of the movement of Ba atom along the dimer row. On the other hand, in the case of Ba adsorption on a monohydrogenated Si(100)2×1 surface, Ba atoms make clusters, particularly at defect sites. In addition, Ba clusters can move across the dimer row.

Hydrogen termination and electron emission from CVD diamond surfaces: a combined secondary electron emission, photoelectron emission microscopy, photoelectron yield, and field emission study

Abstract The effect of hydrogen termination on the electron emission properties of CVD diamond surfaces is investigated. Three kinds of electron emission process, namely secondary electron emission (SEM), photoelectron emission, and field emission are compared on hydrogen free and hydrogen terminated surfaces. Electron beam stimulated desorption was employed to desorb hydrogen from the diamond surface and to pattern H-free areas on otherwise H-covered surfaces. The hydrogen terminated areas give strong electron emission in contrast to the hydrogen free surfaces for all emission processes studied. In particular, the hydrogen free patterns are imaged with comparable contrast by SEM and photoelectron emission microscopy (PEEM). This indicates that the hydrogen termination on diamond surfaces reduces the energy barrier for electron emission by lowering the electron affinity of diamond surface. This is confirmed by a drastic difference in the onset for field emission between the hydrogenated and hydrogen free parts of the same CVD diamond film. It is further demonstrated by yield spectroscopy that the threshold for electron emission below the gap of diamond is lowered by the hydrogenation process.

Nanoindentation of silicon surfaces: Molecular-dynamics simulations of atomic force microscopy

We investigate the atomic-scale details of atomic force microscopy through a quasistatic molecular dynamics simulation together with a density-functional-based tight-binding method. The changes in the AFM tip shape, the size of the tip-sample contact area, as well as the microscopic hardness and Young's moduli of silicon ${111},{110},{100}$ surfaces are studied. Furthermore, the effects of hydrogen termination of the surface and of subsurface vacancies on hardness and Young's modulus are discussed.

The effect of hydrogen termination on In growth on Si(100) surface

We have investigated the effect of hydrogen termination on the initial stage of In growth on Si(100) surface at room temperature using time-of-flight impact collision ion scattering spectroscopy (TOF-ICISS) and low-energy electron diffraction (LEED). In this study, we found that In thin films grown on both clean and hydrogen-terminated Si(100)1×1 surfaces showed quite different results. The In thin film on the clean Si(100)2×1 surface epitaxially grows with the orientation of In(100)[011]//Si(100)[011]. On the contrary, the In thin film on the hydrogen-terminated Si(100)1×1 surface grows as a polycrystalline film. In other words, epitaxial growth of In thin films is disrupted by the presence of hydrogen atoms residing at the interface between the films and Si substrate. The growth mode of In thin films grown on both surfaces is SK growth mode, which indicates that the growth mode is not changed by hydrogen termination.

STM observation of Ag clustering on hydrogen-terminated Si(100) surfaces

The effect of hydrogen termination on Si(100)-2 × 1 surfaces upon Ag deposition at room temperature (RT) and high temperature (350°C) has been investigated by a scanning tunneling microscopy. The results are also compared with those on clean Si(100)-2 × 1 surfaces. When Ag was deposited at RT, small Ag clusters formed on the hydrogen-terminated surface, in contrast that scattered and relatively individual Ag atoms formed on a clean Si(100)-2 × 1 surface. As increasing the substrate temperature, the size of Ag clusters became larger and the shape gradually changed to rectangular, whose edges were parallel to [011] and [01 3 ] directions. Structural models for these surfaces are also proposed.

Effect of hydrogen termination on the work of adhesion between rough polycrystalline silicon surfaces

A novel micromachined test structure has been used to measure the work of adhesion between polycrystalline silicon surfaces. The effects of several surface treatments, including a hydrogen- and an ammonium-fluoride-induced hydrogen termination and a hydrogen peroxide chemical oxidation, have been investigated with these test structures. A reduction in the average apparent work of adhesion by a factor of 2000 has been observed on the NH4F-treated surface compared to the oxide-coated surface. By using x-ray photoelectron spectroscopy and atomic force microscopy, the observed reduction is traced to the combined effect of the surface chemistry and topography. This work demonstrates that a hydrophobic, rough surface provides a significant reduction of the apparent work of adhesion in polysilicon micromachined devices.

Effect of hydrogen termination and electron irradiation on the sticking probability of Sb on Si(100) surfaces exposed to Sb4

The controlled placement of dopant atoms in all three dimensions of a host semiconductor would enable production of a variety of novel devices. We investigate the use of hydrogen adsorption and electron-beam irradiation to achieve selective deposition of Sb on Si. The retention of Sb after annealing to 570 K on a hydrogen-terminated Si(100) surface is enhanced in those areas that have been electron irradiated either before or after exposure to Sb4. The maximum contrast ratio is ≊2:1 for an electron dose of 0.05 C/cm−2.

Photochemical Etching Effects on Optical Properties of Porous Silicon

ABSTRACTWe have studied effects of hydrogen-termination on optical properties of porous Si. The hydrogen concentration in the samples was controlled by photochemical etching after the electrochemical anodization. Transmission electron microscopy examination shows that the size of Si crystallites in porous silicon ranges from 3 to 10 nm and no significant size changes occur by the photochemical etching process. The PL spectra, the PL excitation spectra, and the picosecond PL decay rate were sensitive to the photochemical etching process. Spectroscopic analysis suggests that the radiative recombination occurs at the near-surface region of the Si crystallites.