Properties of self-organized SiGe nanostructures formed by ion implantation

Properties of self-organized SiGe quantum dots formed for the first time by ion implantation of Ge ions into Si are studied using Auger electron spectroscopy, atomic-force microscopy, and scanning electron microscopy. It is found that a spatially correlated distribution of Ge atoms is observed in Si layers implanted with Ge ions after subsequent annealing of these layers. As a result, nanometer-sized regions enriched with germanium are formed; germanium concentration in these regions is 10–12% higher than that in the surrounding matrix of the SiGe solid solution. Optical properties of the layers with SiGe quantum dots were studied using Raman scattering and photoluminescence. An intense photoluminescence peak is observed in the wavelength region of 1.54–1.58 μm at room temperature. __________ Translated from Fizika i Tekhnika Poluprovodnikov, Vol. 38, No. 5, 2004, pp. 593–597. Original Russian Text Copyright ? 2004 by Parkhomenko, Belogorokhov, Gerasimenko, Irzhak, Lisachenko.     

X-ray topography analysis of acoustic wave fields in the SAW-resonator structures

The formation of fields of standing surface acoustic waves (SAW) in LiNbO3 and La3Ga5SiO14 (LGS) crystals was studied by high-resolution topography method on a laboratory X-ray source. The fields of standing SAW were formed using SAW-resonator structures consisting of interdigital transducer (IDT) and reflecting gratings. The SAW amplitudes and power flow angles were measured by X-ray topography, diffraction in acoustic beam was visualized, and the SAW interaction with the crystal structure defects was studied.     

Structure and thermomechanical properties of fast-quenched Ti<Subscript>2</Subscript>NiCu alloy ribbons with various crystalline phase fractions obtained by means of annealing by electric current

New promising functional materials—amorphous-crystalline fast-quenched Ti₂NiCu alloys exhibiting the shape memory effect (SME)—are studied. A method for annealing amorphous alloys by electric current pulses is proposed. This method allows one to obtain the needed degree of crystallinity. It is demonstrated that a microcrystalline structure with spherical grains exists in amorphous-crystalline samples. These grains increase in size from 150 nm to 3.2 μm as the degree of annealing increases. The SME is not observed in nontreated samples and is clearly manifested in completely annealed samples. A two-way SME and a trend toward lowering of the martensitic transition temperature are observed in partially annealed samples.     

Preparation of Pr- and Dy-Doped Rb1 − x M x Pb2Cl5 − y Br y (M = K,Cs) crystals

We have demonstrated for the first time the possibility of preparing high-purity and praseodymium- and dysprosium-doped solid solutions based on lead halides and alkali metals: Rb_{1 ? x} Cs _x Pb₂Cl₅, Rb_{1 ? x} Cs _x Pb₂Br₅, Rb_{1 ? x} K _x Pb₂Cl₅, and RbPb₂Cl_{5 ? y} Br _y . According to X-ray diffraction data, Rb_{1 ? x} Cs _x Pb₂Cl₅ and Rb_{1 ? x} Cs _x Pb₂Br₅ crystals in the solid solution range are isostructural with the constituent double salts RbPb₂Cl₅ and RbPb₂Br₅, respectively. The double salt Rb_0.5K_0.5Pb₂Cl₅ is isostructural with KPb₂Cl₅, and the double mixed salt RbPb₂Cl_2.5Br_2.5 is isostructural with RbPb₂Br₅. The Pr³⁺ and Dy³⁺ concentrations in crystals of the solid solutions and mixed salts were determined by inductively coupled plasma mass spectrometry (ICP-MS). In the Rb_{1 ? x} (Cs, K) _x Pb₂Hal₅ (Hal = Cl, Br) solid solutions, the dopants were observed to be nonuniformly distributed over the host. According to ICP-MS analysis data and absorption spectra, the Pr³⁺ and Dy³⁺ concentrations in the RbPbCl_2.5Br_2.5 crystals were higher than those in RbPb₂Br₅.     

Giant reversible deformations in a shape-memory composite material

New scheme of a functional composite material based on a shape memory alloy has been developed and experimentally tested. The proposed scheme ensures a giant reversible bending deformaion using only one-way shape memory. The scheme has been experimentally implemented on models manufactured by galvanic deposition of nickel onto preliminarily pseudoplastically deformed rapidly quenched Ti₅₀Ni₂₅Cu₂₅ alloy ribbons. The proposed scheme is especially promising for applications in micro- and nanomechanics. In particular, prototype nanotweezers have been manufactured on this basis with record small dimensions of 12 × 3 × 1 μm and a 500-nm-thick shape-memory layer, which is capable of manipulating objects with sizes from 10 to 1000 nm. Controlled deformation of nanotweezers was achieved by heating them using semiconductor laser radiation in a vacuum chamber of scanning ion-probe microscope.     

Relaxation Properties of the Rouse Chain with Inhomogeneous Links

The relaxation properties of the Rouse chain with inhomogeneous links have been investigated. The problem has been solved by direct integration of systems of differentialdifference equations which describe the relaxations of the chain length and stress. It has been shown that these two processes are different in both the set of relaxation modes and the characteristic of the spectrum. The influence of the chain structure on these parameters has been demonstrated. The effect of packing of the relaxation modes has been revealed; it appears on introduction of links with an increased coefficient of friction into the chain and manifests itself in the fact that the highfrequency modes come closer together and even merge, so that their total number becomes substantially smaller than that in the case of the Rouse model.     

Actuators based on composite material with shape-memory effect

A new scheme of composite functional material based on an alloy exhibiting a shape-memory effect (SME) is proposed. The scheme provides for a giant reversible bending deformation with the use of only “one-way”-SME alloy. An experiment was performed with the use of actuator models manufactured by gluing together the rapidly quenched ribbons and electroplating the pseudoplastically predeformed ribbons of the alloy with nickel. It is shown that the theoretical estimates of the bending moment developed by the actuator and of the reversible deformations of the actuator are in good agreement with the results of the model experiments. The prospects for the use of the new scheme in micro- and nanomechanics are considered. Actuators with record small overall dimensions have been manufactured by the focused ion-beam technique.     

Promising materials of acoustoelectronics

The results of the investigation of multicomponent piezoelectric crystals of the group of galliumlanthanum silicate (langasite) are presented. The synthesis processes and the structure of crystals are investigated. The acoustic properties of the crystals are investigated using X-ray topography and diffractometry. The possibility of applying these piezoelectric crystals in high-temperature sensor devices based on surface acoustic waves is shown.