R Ciach

Growth of III–V semiconductor layers on Si patterned substrates

Abstract Patterned unheated Si{100} substrates in the form of the regular tetragonal pyramids and a structure like hemispherical plates have been found to be effective for a pulse vacuum thermal deposition (pulse-VTD) of GaAs and GaP thin layers (50–500 nm). The effect of the pulse-VTD technological parameters (pulse duration, pulse period, pulse number, pulse current) and the features of the substrate patterns (terraces, steps, kinks, sponges) on the morphology, the composition and the crystallinity of GaAs and GaP layers have been characterized by scanning electron microscopy, electron X-ray analysis and electron diffraction.

PRE-AGEING OF ALSICUMG ALLOYS IN RELATION TO STRUCTURE AND MECHANICAL PROPERTIES

Abstract The effect of magnesium addition to the AlSi9Cu3.5 alloy on the hardening and precipitates morphology during ageing at RT, 160°C or two stage ageing (TSA) was studied using TEM and XSAS methods. It was found that only alloys with Mg addition harden during RT ageing and they also attain the highest hardness maximum at 160°C or during TSA. Two types of precipitates (starting from 0.4 and 1.2 nm) were identified during ageing at RT using XSAS method. They cause streaks in the electron diffraction patterns. In alloys aged at 160°C with Mg addition the S′ phase was identified using lattice imaging technique in addition to the θ ′ plates formed during ageing of the ternary AlSiCu alloy.

Thermostability of physical properties of cadmium telluride crystals

Time-dependent changes of electrical properties are investigated in the range of relative low heating temperatures (Ta 320 to 450 K) for undoped p-CdTe grown by various methods. It is established that the character and direction of the observed changes depend on the level of uncontrolled impurities (Cu preferably), their charge state and the association degree of impurities with intrinsic (VCd) defects. CdTe:Ge (Sn,Pb) crystals are characterized with a high thermostability of electrical properties. q 2000 Elsevier Science S.A. All rights reserved.

Thin films of HgCdTe on silicon surfaces

Thin (about 300 nm and less) HgCdTe and CdTe films have been deposited on Si flat and anisotropically etched microrelief surfaces by YAG:Nd3+ pulsed laser at various substrate temperatures in the range from 323 K to 423 K with 100 laser shots. These films and HgCdTe/Si heterosystems were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and current–voltage characteristics (CVC) analyses. It has been shown that under above conditions laser layer deposition method forms polycrystal films of CdTe, CdHgTe both for microrelief and flat Si substrates in the low temperature range

PLD of HgCdTe on two kinds of Si substrate

Abstract Films of HgCdTe have been obtained by pulse laser deposition method in dynamic vacuum (pressure∼10 −6 Torr) at 293–543 K. Two different kinds of Si surface were used as substrate: (a) flat standard polished {100} surface and (b) anisotropically chemically etched patterned surface. The results of a scanning electron microscopy investigation, electron probe microanalysis and I – V characteristic measurements showed a strong influence of the substrate kind on the morphology, composition, growth mode, growth defects and transport of HgCdTe/Si heterostructure.

Probe microanalysis investigation and electroreflectance spectroscopy of Hg1−xCdxTe PLD films on silicon patterned substrates

Abstract Hg1−xCdxTe films were prepared on Si-patterned substrates by the pulse laser deposition technique from a Hg1−xCdxTe target (x≈0.2). The effects of different substrate temperatures, ranging from 293 to 543 K, different laser shots number in the range of 10–380, and the morphological type of the patterned substrate on the x-composition of films were studied by electron probe microanalysis (EPMA) and electroreflectance (ER) spectroscopy. The correlation between a film composition measured by EPMA and one determined from ER spectra data was observed.

Some aspects of solidification and homogenisation of Mg–Ag alloys

Abstract The model of non-equilibrium solidification based on assumption of full diffusion in liquid and its lack in the solid state has been adopted in Krupkowskis evaluation to Mg–Ag alloys to describe maximum microsegregation of components in the α solid solution resulting in appearance of maximum amounts of non-equilibrium phases. The results were then compared with experimental in MgAg 2.5 wt.% alloys with and without addition of 0.6 wt.% zirconium and 2.5 wt% neodymium (RE) by means of scanning and transmission electron microscopy equipped with an energy dispersive spectrometer. It was found that zirconium entered the solid solution, while neodymium appeared as a net of the Mg–Ag–Nd ternary eutectic.The homogenisation process has been studied based on hardness measurements and structure analysis. The times and temperatures of homogenisation to receive uniform distribution of components in the solid solution have been chosen neglecting the remaining eutectic precipitates due to economical reasons.

Electrical behaviour of HgCdTe/Si heterostructures

HgCdTe/Si heterostructures (HSs) were obtained by pulsed laser deposition (PLD) on Si (p- or n-type) flat and patterned (pyramid-like and plate-like) substrate from p- or n-type HgCdTe target. The I–V characteristics of p–n and isotype HSs were investigated by the differential approach. This approach is based on monitoring of differential slope α of the I–V characteristics in log–log plot (α=d lgI/d lgV). Influence of the substrate kind (flat, pyramid-like or plate-like), type of conductivity, type of HS (p–n or isotype) and substrate resistivity were studied. In all cases, the main feature of the I–V characteristics behaviour was α=3/2. It means that the bimolecular recombination is the main recombination mechanism in all HSs types.

SEM observation, photoconductivity investigation and I–V study of Si structures with patterned morphology for solar irradiance detection

Abstract Different types of silicon modified patterned substrates with and without p–n-junction were applied as a way for improving solar cells performance in order to prevent the light losses: (i) pyramid like (textured) surfaces (PrS); (ii) hemispherical plate like surface forms (PIS); (iii) dendritic structures (DS); (iv) porous morphology (LEPSi); (v) combinations of a textured surface with a porous one, etc. To realize them the anisotropical chemical and electrochemical etching in various etched mixtures and regimes, epitaxy and ion implantation were performed. Using scanning electron microscopy, spectral photoresponse measurements and current–voltage data, the morphological design, the variations in the photosensitivity, the wavelength peak position and the recombination parameters induced by the patterned processing and their influence for achieving the successful Si solar irradiance detection have been studied and analysed.

Silicon based multilayer structures prepared by reactive pulsed laser deposition

Nanocrystalline-Si (nc-Si) films were prepared with reactive pulse laser deposition (during the deposition, oxygen or nitrogen gas was introduced into the chamber). The effect of the formation conditions on the optical and photoluminescence properties of films have been analysed. The electronography of cross-sections was performed by transmission electron microscope. It was concluded that pulsed laser deposition is a method to produce the Si low-dimensional material.