E. Yu. Zykova

Features of sputtering of nitrides and their components

The sputtering behaviour of hexagonal or wurtzite polycrystal nitrides of boron, aluminium, and gallium was explored employing methods of molecular dynamics. The sputtering yield Y of nitrides and the average energy Ē 1 of emitted particles were studied as dependent on the mass m 1 of bombarding He, Li, B, N, Ne, Al, Ar, Ni, Ga, Kr, and Xe ions with the initial energy E 0 between 200 and 10,000 eV. Y(m 1) and Ē 1(m 1) were researched upon for preferential sputtering of nitride components at low E 0. It was revealed that the ratio between the sputtering yield of the light component and that of the heavy one depends on ion energy and mass. At E 0=200 eV and m 1=40, the ratio for BN, AlN, and GaN amounts to 1.2, 2.2, and 2.4, respectively. For nitride components, an anomalous dependence of sputtering on ion mass was found, its maximum occurring at a certain ratio m 2/m 1, where m 2 is the averagè mass of two nitride components.

Experimental study and computer simulation of AlN and BN sputtering

The radiation stability of AlN polycrystals with wurzite structure and BN polycrystals with hexagonal and rhombohedral structure irradiated with Ar+ and Kr+ ions was studied experimentally and by computer simulation for normal and oblique incidence. Absolute values of the sputtering yield from AlN were measured for the first time and used to choose the binding energy in the simulation model. Radiation strength of BN to ion irradiation is much higher than that of AlN. The effect of low-energy electron irradiation on surface structure was studied. It was found that, in contrast with BN, the surface of AlN is not modified by electrons.

Formation of aluminum island films under electron irradiation of a sapphire surface

The present paper is devoted to experimental investigation of electron-stimulated desorption from a single-crystal sapphire surface. Using Auger electron spectroscopy metallization of the sapphire surface, the character of which is dependent on the electron beam parameters, is observed under low-energy electron bombardment,. Using atomic-force microscopy, images of metal island films with a diameter of 50–100 nm are obtained.

Desorption of atomic particles and surface modification of fluorides under electron irradiation

Low-energy electron stimulated desorption (ESD) and surface modifications of CaF2 and BaF2 single crystals were experimentally studied at different surface temperatures. A technique based on the dependence of the surface composition on the electron irradiation dose was applied to determining the ESD cross section. The surface composition was measured by Auger electron spectroscopy (AES). Surface topography was examined by atomic force microscopy (AFM). The ESD mechanisms for fluorides were discussed.

On the Energy Spectra of Secondary Ions Emitted from Silicon and Graphite Single Crystals

Secondary ion emission from silicon and graphite single crystals bombarded by argon ions with energies E0 varied from 1 to 10 keV at various angles of incidence α has been studied. The evolution of the energy spectra of C+ and Si+ secondary ions has been traced in which the positions of maxima (Emax) shift toward higher secondary-ion energies E1 with increasing polar emission angle θ (measured from the normal to the sample surface). The opposite trend has been observed for ions emitted from single crystals heated to several hundred degrees Centigrade; the Emax values initially remain unchanged and then shift toward lower energies E1 with increasing angle θ. It is established that the magnitude and position of a peak in the energy spectrum of secondary C+ ions is virtually independent of E0, angle α, and the surface relief of the sample (in the E0 and α intervals studied). Unusual oscillating energy distributions are discussed, which have been observed for secondary ions emitted from silicon (111) and layered graphite (0001) faces. Numerical simulations of secondary ion sputtering and charge exchange have been performed. A comparison of the measured and calculated data for graphite crystals has shown that C+ ions are formed as a result of charge exchange between secondary ions and bombarding Ar+ ions, which takes place both outside and inside the target. This substantially differs from the ion sputtering process in metals and must be taken into account when analyzing secondary ion emission mechanisms and in practical applications of secondary-ion mass spectrometry.

Sputtering of boron nitride single crystals of different structure

Results obtained in studying the sputtering of single crystals of hexagonal, rhombohedral, and cubic boron nitride modifications by computer simulations are reported. Data on sputtering the (0001) face of BN in two graphite-like modifications and the (111) face of BN crystals with a cubic lattice are presented. The energy and angular dependences of the sputtering yields and spatial and energy distributions of sputtered particles are considered for the cases of normal and oblique ion incidence. Specific features of the anisotropy of spatial distributions of sputtered particles and mechanisms of their formations are analyzed.

Change of Auger-electron emission from Ni-Pd alloys under magnetic phase transition

The change of Auger-electron emission from polycrystals of disordered ferromagnetic NiPd3 and Ni3Pd alloys, under ferro- to paramagnetic transition, has been studied experimentally. It has been shown that the intensity of the Auger-lines, which are formed because of transition of valent zone 3d3/2 and 3d5/2 electrons, has local maxima near the Curie point T C for the alloys. Thus, the sensitivity of Auger-electron emission to a magnetic state of the alloy has been established.

Electron-beam charging of dielectrics preirradiated with moderate-energy ions and electrons

The effects of charging of dielectric targets irradiated with moderate-energy electrons in a scanning electron microscope are examined. Considerable differences in the kinetics of charging of the reference samples and the samples preirradiated with ions and electrons are reported. These differences are attributed to the processes of radiation-induced defect formation in Al2O3 (sapphire) and SiO2 that are, however, dissimilar in nature. The contributions of surface structure modification and changes in the electrophysical parameters of the surface (specifically, the charge spreading effect) are revealed. Critical doses of irradiation with Ar+ ions and electrons inducing active defect formation in dielectric targets and critical values of internal charge fields producing a significant contribution to the temporal parameters of Al2O3 and SiO2 charging are determined.

Calculation of the electronic structure of metal island films

The aim of our paper is to study the electronic structure of metal island films as examples of a nanosystem. Because the electronic structure is discrete, the charge exchange between atomic particles and nanosystems exhibits quantum-dimensional effects. We calculated the electronic structure of thin island films, which is required for solving and analyzing the problem of charge exchange with the film. The typical island dimensions are also estimated; in the case of dimensions exceeding them, the discreteness of the electronic structure becomes unimportant and quantum-dimensional effects disappear.

Radiation resistance of boron nitride and related ceramics to low-energy electron irradiation

The radiation resistance of heat-proof ceramics based on boron nitride (BN + Si3N4 and BN + SiO2), which are proposed to be used as structural materials in space ion engines, to low-energy electron irradiation has been investigated.