Advanced Materials Research Vol. 1117

Abstract: Quasiperiodic microstructures are formed on the surfaces of metals under irradiation with high-power femtosecond laser pulses. Interpretation of microstructures as a result of interference of the incident plane wave and surface waves leads to the logical conclusion about the relationship of dislocations in the interference fringes with optical vortices in surface wave. Other peculiarities observed in these structures contain different periods and nanogranular fine structure. It is demonstrated that such laser-induced structures can find applications for surface plasmon excitation and surface enhanced Raman scattering.

Abstract: It was established that irradiation of a semiconductor by nanosecond laser leads to drift of the impurity atoms. The direction of the drift depends on relation between covalent radius of the impurity and of the basic substance atoms. This effect was shown for a wide class of semiconductors, such as: Si, Ge, InSb, GaAs, CdTe, Cd_xZn_1-xTe. This is due to a laser thermal shock effect connected with action of high temperature and pressure gradients formed by strong absorbed nanosecond laser pulse. A new concept was proposed, and the technology has been developed of laser-induced (YAG: Nd ⁺³, wavelength l= 0.532 mm, pulse duration τ_p = 10 ns) nano-fragmentation of metal film, for example, Au with an average size of fragments <δ> = 80 nm, and the concentration on the surface <n> = 2.5×10⁹ cm^-2. The fragmentation is realized by the self organization of surface plasmon-polariton subsystem excited by high power laser pulses at a surface plasmon-polariton resonance. It was shown that the proposed method provides by laser-assisted fragmentation of the metal film (Au) in conditions of the resonance, decomposition of the nanofragments from the substrate, their transfer through an air gap, and implantation in a polymer layer on a separate surface at the same laser pulse.

Abstract: The photoconductivity (PC) spectra of CdZnTe (CZT) semiconductor solid solutions obtained from different manufacturers were investigated before and after irradiation with nanosecond laser pulses. Depending of energy density, irradiation of CZT crystals resulted in an increase in the photosensitivity, high-energy shift of the PC spectrum maximum and transformation of its profile. Laser processing with the certain energy densities improved homogeneity in the crystal surface area and provided equalization of structural characteristics in the surface region and bulk of the samples. Irradiation of CZT crystals pre-coated with an In electrode film caused rectification in the I-V characteristics because of the formation of a barrier structure. The application of the obtained In/CZT/Au diodes with low leakage current as X/γ-ray detectors is considered.

Abstract: The enhancement of CdZnTe crystal resistivity by λ=1064nm Nd:YAG laser radiation was shown. This effect is explained by compensation of cadmium vacancy (V_Cd) by indium atoms due to a laser-induced temperature gradient around Te inclusions. The temperature gradient is caused by the selective absorption of the laser radiation by the Te inclusions.

Abstract: Irradiation of SiGe-on-Si structures by pulsed Nd:YAG laser with intensities 1.0 MW/cm² leads to the formation of Ge nanocones. As a result increases the surface photovoltage (SPV) signal up to 10 times. The SPV decays do not speed up with the radiation, thus indicating that the laser treatments do not cause an increase in the concentration of recombination centers at interfaces. Therefore the fabrication technique proposes here may be considered to be an effective approach of producing cost-competitive photosensors based on SiGe/Si.

Abstract: Studying atomic clusters, their chemical composition can be find by time-of-flight mass spectroscopy even for a miserable quantity of the sample, while their structure determination requires either their production in enough quantity that can be problematic for new substances, or usage of quantum chemical calculations otherwise. However, the result of the calculations depends on the method used. It is suggested in this report to use a correlation between the abundances of the clusters in the mass spectrum and their calculated binding energies as a criterion for selection of an appropriate calculation method. This approach is applied for the case of (ZnO)_n and (ZnS)_n clusters of n = 12 and 13.

Abstract: In order to investigate impact production of carbonaceous molecules by asteroid’s impact, simulation experiment is carried out using a 2-stage light gas-gun. A small polycarbonate bullet is injected into a pressurized chamber with 1 atm of nitrogen gas, to collide with a target. Strong emissions of CN and C2 molecules are measured, and CN rotational temperature is evaluated. In the produced soot, production of fullerenes, nanotubes, metal-encapsulated particles, balloon-like nano-carbons and amino acids is confirmed.

Abstract: Adsorption of pyrrole on the Si(111)-7×7 surface was investigated using scanning tunneling microscopy (STM). Template-induced molecular corral structure was observed at room temperature though the N-H bond cleavage. At the substrate temperature of 130 °C, the pyrrolyl adsorbates were observed by STM with reserving the 7×7 substrate. However, the self-assembly of the molecular corral structure was disarranged at 130 °C. Then, pyrrolyl group was decomposed or desorbed from the surface at the substrate temperature of 200 °C. The defect-induced attachment of pyrrole was also observed.

Abstract: The electrically thin absorber of electromagnetic waves is under study. We proposed a new concept of the perfect absorber which consists from a single layer of the smooth double-turn helices. This allows one to design an absorber with unprecedentedly small thickness. Simple and smooth shape of the helices makes them more preferable from experimental point of view in comparison to other chiral particles. The absorber implies absence of a ground plane. High efficiency of the realized structure in the S band is demonstrated.