KEYWORDS: Laser ablation, Cadmium, Chemical species, Tellurium, Ions, High power lasers, Plasma, Emission spectroscopy, Laser damage threshold, Thin films
Investigations of parameters of the ablation specie produced by laser ablation from the CdTe targets
were carried out. Optical emission spectroscopy and quadrupole mass spectroscopy methods were used for
measurement of ablation species properties. Quantitative and qualitative parameters of ablation species were
studied by optical emission spectroscopy. The dependences of the velocities of ablation components and they
kinetic energies on the ablation parameters were established, as well. It was found that the ablation of CdTe
targets by laser pulses with threshold power possessed a congruent character. In this case, analysis of mass-spectra
of ablation species generated by high-power laser pulse shown that it was consisted only Cd and Te
atoms, but with various degrees of ionization state. We established that parameters of ablation species have a
strong the dependence on laser pulses regimes and parameters of background ambience.
In this paper we report about investigation of laser and laser-magnetron fabrication of nitride thin films (AlN, AlN:Mn, GaN, GaN:Zn, GaN:Cr) in quasi-closed chemically active ambience. On the base of conducted investigations it was found that the mode of deposition from both excited atoms and ions and chemically-active gas (nitrogen) can be realized depending on laser pulse energy, nitrogen pressure in the chamber and target-substrate distance what results in films formation with minimal deviation from stoichiometrical composition. Films crystallinity level and structure perfection depend on their growth rate on substrate surface. The complex of experimental and theoretical works on study of mechanical pressure in system AlN-Al2O3, is carried out by the analysis of elastic deformations. Is established, that the condensed layers as by laser and laser-magnetron methods were in is intense the deformed condition of compression. Basic regularities of pulse laser crystallization and cathodoluminescent brightness alteration dependencies on energy density of laser annealing were studied.
The work deals with the experimental researches of the processes of structural defects generation in (Cd,Hg)Te epitaxial layers on the CdTe substrates and CdTe monocrystals after impulsive laser processing and their influence on the mechanical, optical and galvanomagnetical properties. In the experiments we used the ruby laser radiation with energy density, changed in the range of 1,5-15 J/sq.cm. The duration of the laser impulses was about 1,5 ms and 20 ns. Changes in the chemical composition of the irradiated surface have been analyzed by Auger electron spectroscopy. The zones with increased defects concentration were determined by the method of selective chemical etching. It was shown, that the impulsive laser processing results in both the essential redistribution of the components concentration and generation of the linear and dot defects in the near-surface crystal layers, excited by the laser irradiation. Microhardness of the surface, irradiated with the laser without preliminary heating increases in the average on 20-30%. The photoluminescent properties of the laser modified cadmium-telluride samples were investigated in the spectral range of 650-1000 nm. After the laser irradiation of the samples the redistribution of the intensity of the luminescence bands and emergence of new band was observed in the region of 840 nm, when the temperature of samples was about 4,2 K. The essential growth of the spectral band intensity with a maximum within the range of 875-885 nm, when T= 77 K, was observed as well. Diminution of the life time of non-equilibrium charge carriers in a defective zone creates the premises to the magnetoconcentration effect origin in the crossed electrical and magnetic fields. The perspective of usage of such (Cd,Hg)Te structures as infrared and magnetic field sensors is shown.
In order to form flat-panel displays with a high resolution property, the phosphor layer should possess considerable electrical conductivity and thermal stability. Thin phosphor films of zinc silicates, rare earth galats and/or multilayer system on their ground are known to satisfy these very requirements. The authors choose the following compounds of ZnSiO4:Ti, ZnSiO4:Mn, Zn0.4Gd1.6O3:Eu, KGa5O8:Mn with the corresponding color gamma luminescence as the targets for laser pulse deposition based on the above mentioned reasons. The main results on the research physical-technological conditions of the thin phosphor compound film synthesis of the of ZnSiO4:Ti, ZnSiO4:Mn, Zn0.4Gd1.6O3:Eu, KGa5O8:Mn obtained by means of the reactive laser pulse evaporating with the help of quasi-closed reactive ambience are given in this work.
This paper examines the experimental researches of structure defect generation in (Cd, Hg)Te epitaxial layers on CdTe substrates and CdTe mono-crystals after pulse laser treatment and the influence of these defects on mechanical, optical and galvano-magnetic properties of the samples. In the experiments we used the ruby laser radiation with energy density changed in the range 1.5-15 J/cm2. The duration of laser pulses was about 1.5 ms. Changes in the chemical composition of the irradiated surface have been analyzed by the Auger electron spectroscopy. The zones with increased defect concentration were determined by the method of the selective chemical etching. It has been determined that the pulse laser processing results in both the essential redistribution of the component concentration and generation of the point and extended defects in near-surface crystal layers excited by laser irradiation. After the laser irradiation of the samples the redistribution of the intensity of the luminescence bands and emergence of a new band were observed over the band 840 nm at the temperature of samples about 4.2 K. The essential growth of the spectral band intensity with a maximum within the band 875-885 nm at T equals K has been observed as well.
In this paper we report on the results of experimental investigations of processes of pulse laser reactive deposition and structure formation and characteristics of AlN, AlN:Mn, GaN, GaN:Zn, GaN:Mn, GaN:Cr, MgSiN2:Ti, SrSiN2:Eu thin films which have been condensed from laser erosion plasma into reactive atmosphere (nitrogen).
Experimental investigations of (Cd,Hg)Te have been performed with the use of ns- and ms-duration pulses of solid state laser. Changes in the chemical composition of the irradiated surface have been analyzed by means of X-ray photoelectron and Auger electron spectroscopies. Single crystalline HgTe and (Cd,Hg)Te wafers and epitaxial films have been used as the experimental samples. Processes of integral evaporation with generation of a molten zone with thickness up to several micrometers dominate upon ns-pulses irradiation and crystallization follows autoepitaxy laws. There was not observed increase of linear defects density in the layer near surface. Inverse layer depth in n-(Cd,Hg)Te coincides with molten zone. In the case of ms-pulses the influenced zone is several tenth micrometers thick. Irradiation of the samples at T equals 500 - 600 K in saturated Hg vapor completely suppresses the change of the surface composition. Heating of (Cd,Hg)Te sample leads to generation of a great number of acceptor-type native defects. As a results p-n junctions are formed in n-(Cd,Hg)Te by pulsed laser irradiation.
The article sets out to investigate spatial-time and spectral characteristics of laser erosive vapor-plasma torch (EVT), formed at the vaporization of mercury chalcogenines targets. Its influence on the synthesis processes of HgTe and CdHgTe layers, condensed in mercury vapor, is described. It is shown that the laser radiation flux density and Hg vapor pressure in the reaction chamber are dominating factors which determine the character of gas-dynamic spread and EVT composition of mercury chalcogenides targets.
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