V. V. Naumov

Investigations of nanocrystalline SnS films' surface morphology modification during inductively coupled argon plasma sputtering

In this work the investigations of the morphology, structure and chemical composition of nanocrystalline SnS films grown by hot wall deposition method on glass substrates before and after high-density low-pressure inductively coupled argon plasma sputtering were performed using scanning electron microscopy, x-ray diffraction analysis, Raman spectroscopy, and energy-dispersive x-ray spectroscopy. The phenomenon of the surface smoothing for the SnS films with petal-like nanocrystallites during plasma treatment is described and the low sputtering rate for the studied films is discussed.

Enhancement of the transversal magnetooptical Kerr effect in nanoperforated cobalt films

We present the technology of nanoperforated magnetic structures based on cobalt films deposited onto the surface of a porous aluminum substrate. The structures exhibit a significant (by an order of magnitude) enhancement of the transversal magnetooptical Kerr effect as compared to that in magnetic thin films formed on a usual nonporous substrate. The effect increases with the depth of pores.

Features of CoSi2 phase formation by two-stage rapid thermal annealing of Ti/Co/Ti/Si(100) structures

A method of cobalt disilicide (CoSi2) layer formation proceeding from a Ti(8 nm)/Co(10 nm)/Ti(5 nm)/Si(100) (substrate) structure prepared by magnetron sputtering is described. The initial structure was subjected to two-stage rapid thermal annealing (RTA) in nitrogen, and the samples after each stage were studied by the time-of-flight secondary-ion mass spectrometry, Auger electron spectroscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The RTA-1 stage (550°C, 45 s) resulted in the formation of a sacrificial surface layer of TiNxOy, which gettered residual impurities (O, C, N) from inner interfaces of the initial structure. After the chemical removal of this TiNxOy layer, the enrichment with cobalt at the RTA-2 stage (830°C, 25 s) led to the formation of a low-resistance CoSi2 phase.

Fabrication of porous nanostructured lead chalcogenide semiconductors for modern thermoelectric and optoelectronic applications

Porous structures of lead chalcogenides with porosities of 20-68% and pore dimensions as small as 7-20 nm were fabricated using an anodic electrochemical etching technique applied to epitaxial PbTe and PbSe films on Si. Anodized lead selenide demonstrated two basic types of porous morphology: quasiporous noncontinuous layers and hierarchical porous layers. Lead telluride had a more typical mesoporous morphology, with pores propagating at an angle of 35° to surface, which corresponds to the <100< directions in the epitaxial films and is promising for the fabrication of photonic crystals with Yablonovite-like structure. The sizes of PbTe nanocrystallites in porous layers with high porosity were calculated to be 26 nm, which indicates that quantum confinement conditions are realized in this material. Such low-dimensional morphology of porous lead telluride is prospective for the fabrication of microscale thermoelectric devices with high ZT.

Features of the plasma sputtering of polycrystalline Pb1 − xSnxS films

The processes of the sputtering and modification of surfaces of polycrystalline films of the ternary solid solution Pb1 − xSnxS (x = 0.9–1.0) in a high-density Ar plasma of high-frequency low-pressure inductive discharge are studied. Films with thicknesses of 1–4 μm are grown on glass substrates using the “hot-wall” method and consist of plate-like crystallites. It is established that the sputtering rate for lead-tin sulfide films does not exceed 2.0 nm/s, which is determined by the presence of oxygen-containing compounds on the surfaces. In the case of plate-like crystallites with nanodimensional thicknesses, the effect of smoothing of the developed surfaces of the polycrystalline Pb1 − xSnxS layers during plasma treatment is observed; this is important for fabricating multilayer device structures.

Investigations of the inductively coupled argon plasma sputtering of Pb1 − xSnxTe ternary solid solution

Investigations of the sputtering of films of the Pb1 − xSnxTe ternary solid solution with 0 ≤ x ≤ 1 in RF high-density low-pressure inductively coupled argon plasma have been performed. The effect of a constant sputtering rate with variation in the composition of the semiconductor solid solution for (111)-oriented films with x < 0.6 and of a sputtering rate decrease with the appearance of (100)-oriented crystallites at x > 0.6 is found. The results are analyzed in the context of a model of ternary alloy sputtering based on the Sigmund solid sputtering theory when taking into account the sublimation energies of binary compounds that constitute a solid solution.

Lead selenide nanowire growth by vapor-liquid-solid mechanism under mask during plasma processing

Data on the formation of lead selenide (PbSe) nanowires under a stencil mask during the processing of epitaxial PbSe films in high-density inductively coupled plasma (ICP) of low-pressure argon RF discharge are presented. The nanowires were studied by high-resolution scanning electron microscopy and energy-dispersive X-ray spectroscopy. A physical model is proposed that explains the local formation of PbSe nanowires in terms of their catalytic growth according to the vapor-liquid-solid mechanism.

Control of the formation of ultrathin CoSi2 layers during the rapid thermal annealing of Ti/Co/Ti/Si(100) structures

The initial Ti(8 nm)/Co(10 nm)/Ti(5 nm) structures formed on the Si(100) substrate by magnetron sputtering were subjected to two-stage rapid thermal annealing (RTA) in the nitrogen ambient. The samples of the structures were controlled using the time-of-flight SIMS, the Auger spectroscopy, scanning electron microscopy, X-ray dispersion microprobe analysis, and measurements of the layer resistance at each stage of annealing. At the RTA-1 stage (550°C, 45 s), a sacrificial layer formed on the surface. This layer consisted of the titanium (oxy)nitride coating, into which the residual impurities (O, C, and N) were forced out, and the transient Co-Si-Ti(TiO,TiN) layer with a high cobalt content and a low (trace) titanium content. After the selective removal of this sacrificial layer, the surface composition corresponded to monosilicide CoSi, which transformed into the highly conductive CoSi2 phase at the RTA-2 stage (830°C, 25 s).

Increasing adhesion of metallic films to silicon by ion bombardment during growth

Intense ion bombardment at the initial stage of film growth is used to increase the adhesion of nickel and vanadium films to silicon. The films are deposited by rf magnetron sputtering when a bias potential is applied to a substrate. The adhesion of metallic films to silicon is substantially increased due to active mixing of the contacting materials and the formation of a transition layer with a concentration gradient. A correlation between the adhesion of the films and their crystalline state is revealed.

Application of abnormally high sputtering rate of PbTe(Te) single crystals during inductively coupled argon plasma treatment for fabrication of nanostructures

This paper reports the investigations of the sputtering process of (111) oriented single crystals of PbTe with excess tellurium (4 at.%) in RF high-density low-pressure inductively coupled argon plasma. An increase of 1.6 times the sputtering rate of lead telluride in comparison with the classical case of single-crystal state with a slight deviation from stoichiometry is shown and the explanation of the results is carried out based on the analysis of the crystal point defects. The active sputtering is used in a new approach to form lead telluride nanostructures on oxidized Si substrates via the vapour–liquid–solid (VLS) redeposition mechanism, and the fabrication of PbTe nanocones, nanocubes and nanowires with various geometrical parameters is demonstrated.