H S Tan

XPS studies on nitridation of InP(100) surface by ion beam bombardment

Ion beam nitridation (IBN) of InP at room temperature was studied as a function of both ion incident angle and energy. The InP surfaces were exposed to ion beam in an ultrahigh vacuum environment and the resulting surfaces were characterized in situ by small spot size x-ray photoelectron spectroscopy (XPS) for accurate determination of the surface composition and chemical state. Thin InN reaction layers were formed at all ion incident angles and ion energies whereas the formation of P - N bonds was not observed. However, the degree of nitridation of In decreases with increasing incident angle and ion energy, closely following the reduced incorporation of N at higher angles and ion energies. The variation in nitridation is smaller with ion energy in the 2 - 10 keV range than with ion incident angle. The observed angular and energy dependence of the N incorporation can be explained in terms of sputtering yields, indicating that the growth kinetics can be described as a dynamic process comprising the accumulation of N and sputter removal of the surface layer.

Argon incorporation and silicon carbide formation during low energy argon‐ion bombardment of Si(100)

Argon incorporation and the formation of silicon carbide in Si(100) by low energy Ar+ ion bombardment have been studied by angle‐resolved x‐ray photoelectron spectroscopy (XPS). The bombardment was performed at ion energies of 1, 1.5, and 2 keV and various ion fluences in an ultrahigh vacuum chamber equipped with XPS. The XPS measurements showed that the incorporated Ar concentrations achieved saturation in the near‐surface region at ion bombardment fluences ≳1016 cm−2. The surface Ar concentrations decreased with increasing bombardment energy. No Ar bubbles on the surface of Ar+‐bombarded samples were observed by atomic force microscopy under these experimental conditions suggesting that Ar bubble formation was not the main Ar trapping mechanism in our study. The SiC formation was confirmed by characteristic XPS peaks of Si 2p and C 1s for SiC. The carbide formed at lower ion fluence was of a metastable structure as inferred by XPS. Bombardment at higher ion fluence yielded a stable carbide phase through...

Argon incorporation and surface compositional changes in InP(100) due to low‐energy Ar+ ion bombardment

Angle‐resolved x‐ray photoelectron spectroscopy (ARXPS) has been used to study the Ar incorporation and surface compositional changes in InP(100) after 1–5 keV Ar+ bombardment at various ion fluences. The ARXPS measurements showed that the incorporated Ar concentration achieved saturation at ion bombardment fluences of >1016 cm−2. The surface Ar concentration decreased with increasing bombardment energy. No Ar bubbles were observed by atomic force microscopy, suggesting that Ar bubble formation was not the main Ar trapping mechanism. The altered layers were, on average, In rich up to the sampling depth of the ARXPS technique. However, the altered layers were inhomogeneous as a function of depth and appeared more In rich at the surface than in the subsurface region. The results are compared with those obtained by other authors and discussed in the context of preferential sputtering, radiation‐enhanced diffusion and segregation, and Ar incorporation. Although the altered layers were In rich, a P‐rich phase ...

Multi-black-hole solutions in five dimensions

Using a recently developed generalized Weyl formalism, we construct an asymptotically flat, static vacuum Einstein solution that describes a superposition of multiple five-dimensional Schwarzschild black holes. The spacetime exhibits a

ARXPS analysis of surface compositional change in ion bombarded GaAs (100)

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AUGER ELECTRON SPECTROSCOPY AND X-RAY PHOTOELECTRON SPECTROSCOPY ANALYSIS OF ANGLE OF INCIDENCE EFFECTS OF ION BEAM NITRIDATION OF GAAS

rotational symmetry. It is argued that for certain choices of parameters the black holes are collinear and so may be regarded as a five-dimensional generalization of the Israel-Khan solution. The black holes are kept in equilibrium by membranelike conical singularities along the two rotational axes; however, they still distort one another by their mutual gravitational attraction. We also generalize this solution to one describing multiple charged black holes, with fixed mass-to-charge ratio, in Einstein-Maxwell-dilaton theory.

AES analysis of nitridation of Si(100) by 2–10 keV N+2 ion beams

Angle-resolved x-ray photoelectron spectroscopy (ARXPS) has been used to study surface compositional changes in GaAs (100) as a consequence of 1 to 5 keV ion bombardment. Prior to ion bombardment, the ARXPS measurements showed that neglecting surface contamination, the composition of the GaAs surface was close to its stoichiometric value of 1:1. After ion bombardment, the oxide layer was efficiently removed. At steady state the altered layers induced by 1 - 5 keV ion bombardment were, on average, Ga-rich up to the sampling depth of the ARXPS technique. The ARXPS measurements also showed that the depth profile of the altered layer was a function of ion energy. The altered layer induced by 1 keV ion bombardment was inhomogeneous as a function of depth and appeared richer in Ga on the surface than in the subsurface region, that by 3 keV ion bombardment was homogeneous and that by 5 keV ion bombardment was less Ga-rich on the surface than in the subsurface region. The results are discussed in the context of preferential sputtering, radiation-enhanced diffusion/segregation, and altered layer thickness dependence on ion energy.

AES analysis of silicon nitride formation by 10 keV N+ and N2+ ion implantation

Ion beam nitridation (IBN) of GaAs at room temperature was studied as a function of N 2 + ion incident angle at ion energy of 10 keV. The ion beam bombardment surface area of GaAs was characterized in situ by both Auger electron spectroscopy (AES) and small spot-size x-ray photoelectron spectroscopy (XPS). Thin GaN reaction layers are formed at all N 2 + ion incident angles, whereas the formation of As–N bonds has not been found. However, the degree of nitridation of Ga decreases with increasing incident angle. The observed angular dependence of the N incorporation can be explained in terms of sputtering yield, indicating that the growth kinetics can be described as a dynamic process comprising the accumulation of N and sputter removal of the surface layer. N 2 + ion bombardment causes the depletion of As from the surface region because of the preferential sputtering of As from GaAs. The preferential sputtering of As reduces with increasing N 2 + ion incident angle. The angular dependent behavior of preferential sputtering of As by 10 keV N 2 + ions can be attributed to the angular dependence of GaN surface layer formation.

Exact solutions of a nonpolynomially nonlinear Schrödinger equation

Abstract Ion beam nitridation of Si(100) as a function of N + 2 ion energy in the range of 2–10 keV has been investigated by in-situ Auger electron spectroscopy (AES) analysis and Ar + depth profiling. The AES measurements show that the nitride films formed by 4–10 keV N + 2 ion bombardment are relatively uniform and have a composition of near stoichiometric silicon nitride (Si 3 N 4 ), but that formed by 2 keV N + 2 ion bombardment is N-rich on the film surface. Formation of the surface N-rich film by 2 keV N + 2 ion bombardment can be attributed to radiation-enhanced diffusion of interstitial N atoms and a lower self-sputtering yield. AES depth profile measurements indicate that the thicknesses of nitride films appear to increase with ion energy in the range from 2 to 10 keV and the rate of increase of film thickness is most rapid in the 4–10 keV range. The nitridation reaction process which differs from that of low-energy ( + 2 ion bombardment is explained in terms of ion implantation, physical sputtering, chemical reaction and radiation-enhanced diffusion of interstitial N atoms.

Laser‐induced lattice tensile strain in silicon

Abstract Reactions of N + and N 2 + ions with the Si(100) surface as a function of ion dose and angle of incidence by 10 keV N + and N 2 + bombardment have been studied by in situ Auger electron spectroscopy (AES) analysis. The AES measurements show that a continued exposure of the ion beam to a saturation dose of > 5 × 10 16 N 2 + / cm 2 leads to a surface stoichiometry close to that of Si 3 N 4 . Complete nitridation, i.e. the formation of Si 3 N 4 , could be achieved at incident angles between 0 ° and 30 ° to the surface normal. At incident angles exceeding 30 °, the degree of nitridation decreases. Above 60 ° incident angle, no nitride was found in the near-surface region. A simplified model has been proposed to explain the observed angular dependence. The samples with higher ion doses were also examined by ex situ scanning electron microscopy (SEM). No blister or bubble was found on the surface suggesting that under saturation conditions the self-sputtering of captured nitrogen atoms near the surface by further incoming projectiles is the major contributor to nitrogen removal in our experiment. No pronounced difference between N + and N 2 + bombardment was observed in this experiment.