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In this work we show how ion-beam-induced epitaxial recrystallization plays a role in focused ion-beam (FIB) sputtering of silicon at elevated temperatures. The sputtering process is the key to all high-precision machining of microstructures and nanostructures by FIBs. A fluence-rate effect observed for the sputtering of silicon at elevated temperatures arises from competition between stabilizing interactions between populations of defects produced by consecutive ion impingement (damage buildup) and dynamic self-annealing. By high-resolution transmission electron microscopy analysis we show that the damage, produced by exposure of silicon to a 50 kV focused gallium (Ga) ion beam at elevated target temperatures, departs quite substantially from the expected damage based on the distribution of energy within the substrate due to nuclear stopping. An amorphous layer observed at room temperature is completely absent at higher temperatures. In contrast to FIB exposure at room temperature the implanted layers contain only point defects complexes and dislocations, thus suggesting that defect annealing takes place but it is incomplete. Correlating FIB sputtering experiments and high-resolution transmission electron microscopy, we discuss the lower sputtering yield at elevated target temperatures as the result of a higher surface binding energy of crystalline Si in comparison to amorphous silicon. [ABSTRACT FROM AUTHOR]

A growth diagram for molecular beam epitaxy of AlN on sapphire and 6H-SiC was established using reflection high energy electron diffraction, atomic force microscopy, and Rutherford backscattering spectrometry. In varying the Al/N ratio and growth temperature, distinctive surface morphologies emerge, which are assigned to three regimes of growth, one N-rich (Al/N < 1) and two Al-rich (Al/N > 1) regimes. Under N-rich conditions, AlN films exhibit rough surface morphologies. In contrast, Al-rich conditions produce excellent smooth surface morphologies, but with the constraint of Al droplet formation at very high Al/N ratios and low temperatures. The differentiation between N-rich and Al-rich regimes is given only by the Al/N ratio, while the two Al-rich regimes (intermediate self-regulated and droplet regime) are separated by the boundary line of Al droplet formation. For this boundary an Arrhenius dependence of growth temperature was found, yielding an activation energy of 3.4 ± 0.1 eV. The observed morphology transitions are attributed to varying surface adatom mobilities present under the different Al/N ratios. [ABSTRACT FROM AUTHOR]

Presents a study which examined bias enhanced nucleation of microwave chemical vapor deposited diamond films on silicon. Experimental details; Results; Discussion.

This study reports on the correlation between strain relaxation and nucleation kinetics during the Stranski–Krastanow growth of GaN on (0001)AlN by plasma-assisted molecular beam epitaxy. Using reflection high-energy electron diffraction and real-time desorption mass spectrometry, the strain-related Ga adatom detachment and desorption rates were determined, giving information about the average GaN island nucleation rate. Two different regimes were found: one at low-temperature growth (690S<720 °C), where strain relaxation occurred slowly, yielding impeded island nucleation rates and small island sizes (diameter ∼8–12 nm and height ∼2.3–2.7 nm). In the other, i.e., high-temperature growth regime (TS>720 °C), islands showed an abrupt relaxation mode, accompanied by a fast nucleation rate toward island sizes twice as large. [ABSTRACT FROM AUTHOR]

Epitaxial growth of single crystalline silicon nanowires along the <111> directions was obtained on Si (100) and Si (111) substrates by gold-gallium-nanoparticle-catalyzed chemical vapor deposition with a SiH4 precursor. In comparison to the pure gold catalyst, the proportion of the nanowires growing perpendicular to the substrate is much higher and the wires show almost no kinks. The average diameter is smaller, and the diameter and length distributions are narrowly dispersed. By making a particular choice of growth conditions, it is possible to realize either rodlike or tapered silicon nanowires, which may be desirable for applications as field emitters. [ABSTRACT FROM AUTHOR]

We present a study of the evolution of the Ga adlayer during plasma-assisted molecular-beam epitaxy of (0001) GaN as a function of both Ga flux and growth temperature. In situ quadrupole mass spectrometry was used to quantitatively determine the adsorbed Ga coverage by monitoring its subsequent desorption after GaN growth. Independent of the growth time, the Ga adlayer was found to form steady-state coverages that increase continuously from 0 to 2.5 monolayers when raising the Ga flux from N-rich to moderate Ga-rich growth conditions. At higher Ga fluxes or lower growth temperatures, macroscopic Ga droplets form on top of the Ga adlayer (Ga droplet regime). Based on the temperature dependency for the transition between the Ga adlayer and Ga droplet regime, we determined an apparent activation energy of 3.4 eV, which is discussed with respect to previously reported values. [ABSTRACT FROM AUTHOR]

We present a nucleation study for molecular-beam epitaxial growth of GaN on 6H-SiC and sapphire using Rutherford backscattering, atomic force microscopy, and in situ line-of-sight quadrupole mass spectrometry. Film thickness measurements by Rutherford backscattering reveal a strong deviation from thickness calculations assuming steady-state growth. We differentiate two regimes of growth, initially a highly nonlinear growth mode during island formation and later a linear growth mode after coalescence of islands. The mechanisms leading to the nonlinear behavior are attributed to energy barriers that supress immediate nucleation and provide for a substantial desorption of Ga and N atoms. Employing line-of-sight quadrupole mass spectrometry, we developed a quantitative in situ method to determine the amount of desorbing Ga atoms during the entire GaN growth procedure. The amount of initial GaN desorption in heteroepitaxy is independent of the substrate material and is as high as 8 ± 1.5 nm. [ABSTRACT FROM AUTHOR]