A. Ya. Vinogradov

Intensity of visible and IR emission of intracenter 4f transitions of RE ions in Er- and Tm-doped ZnO films with additional Ag, Li, and N impurities

The use of Ag impurity in Er-doped ZnO films deposited by AC magnetron sputtering with a low growth rate has increased the emission intensity at λ = 1535–1540 nm. An increase in the deposition rate and in the temperature of substrates, as well as the use of Li and N+ impurities, led to a considerable increase in the intensity of the line with λ = 376–379 nm in the case of doping with rare-earth ions (Er, Tm), which makes it possible to use this semiconductor for creation of devices for the short-wavelength spectral region. Introduction of additional impurities in Er-doped ZnO films deposited on bulk ZnO crystals with increasing deposition rate and temperature caused an increase in the intensity of the line with λ = 1535–1540 nm. The photoluminescence spectra of ZnO films doped with Tm (ZnO) exhibited intense emission of lines with λmax = 377 nm.

Effect of ion bombardment on the phase composition and mechanical properties of diamond-like carbon films

It is established that the addition of hydrogen to methane in the reaction mixture upon the fabrication of diamond-like carbon films via the plasma-enhanced chemical vapor deposition method decreases residual stresses in the obtained films and significantly reduces their growth rate. The films were investigated via atomic force microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy. Irradiation of the prepared films with P+ and PF4+ ions results in strong sample swelling with increasing dose, as well as in a decrease in the compressive stress up to transition to tensile one reaching saturation. Moreover, the fraction of sp3 bonds increases with increasing ion dose while the fraction of sp2 bonds decreases symmetrically with the processes proceeding faster upon irradiation with molecular ions. Qualitative mechanisms explaining the experimental results are proposed.

Residual stress in diamond-like carbon films: Role of growth conditions and ion irradiation

The dependence of the internal residual stress in thin diamond-like carbon films grown by the plasma-enhanced chemical vapor deposition technique on the most important growth parameters, namely, the radio-frequency (RF) power and direct-current (DC) bias voltage, was studied. It was shown that the compressive stress reaches its highest value of 2.7 GPa at the low RF power and DC bias values. Both increase and decrease of these parameters result in stress decrease. The stress increases with increase in the growth temperature from 250 to 350°C. Thermal annealing of up to 350°C does not affect the stress value. Subsequent irradiation of the films by In+ and P+ ions with the energy of 350 and 120 keV, respectively, results in the decrease in the compressive stress followed by its inversion to the tensile one. The stress linearly depends on the effective dose of up to 0.5 DPA with the slope of (8.7 ± 1.3) Gpa/DPA.

Ion bombardment of amorphous silicon films during plasma-enhanced chemical vapor deposition in an rf discharge

The characteristics of ion and electron fluxes to the surface of a growing silicon film are investigated in various rf discharge regimes in silane at frequencies of 13.56 MHz and 58 MHz in plasma-enhanced chemical vapor-deposition (PECVD) apparatus. The energy spectra of the ions and electrons bombarding the growing film are measured. The electronic properties of films grown under various degrees of ion bombardment are studied. The correlation of these properties with the ion parameters in the rf discharge plasma during film growth is discussed.

Parameters of ZnO films with p -type conductivity deposited by high-frequency magnetron sputtering

It is demonstrated that a reduction in the defect concentration in ZnO films formed by high-frequency magnetron sputtering allows effective doping with acceptor impurities both in the cation (Li) and anion (N+) sublattices and p-type conductivity with reproducible charge-carrier parameters (concentration and mobility) to be obtained. ZnO films are doped with nitrogen by annealing in a high-frequency gas discharge atmosphere. Hall measurements by the Van der Pauw technique show that the deposition of thin Eu layers on the ZnO film surface increases the concentration and mobility of majority charge carriers. The embedding of metal impurities with different ionic radii (Ag and Au) in the cation sublattice of the ZnO films to compensate misfit stresses makes it possible to enhance the concentration of radiative-recombination centers.

UV and IR emission intensity in ZnO films, nanorods, and bulk single crystals doped with Er and additionally introduced impurities

For ZnO films, nanorods, and bulk single crystals doped with Er+ ions, it is shown that the effect of codopants introduced into the cation and ion sublattices and the observation of a high-intensity emission band at the wavelength λmax = 1535 nm are defined by the local environment of the Er+ ion. Doping of the films and single crystals with Er+ ions by diffusion brings about an infrared (IR) emission band with a low intensity because of an inadequate concentration of impurity ions. The emission intensity of this band can be raised by introducing additional Ag, Au, or N+ impurities into the ZnO films. The UV-emission intensity of the Er-doped films and single crystals at λmax = 368–372 nm is identical to that of the undoped films. ZnO nanorods doped with Er only or together with Al or Ga codopants exhibit only one IR band (at λmax = 1535 nm), whose intensity decreases upon the introduction of codopants. Doping of the nanorods with the N+ gaseous impurity during growth (930 < T < 960°C) and then with the Er+ impurity by diffusion does not yield a substantial increase in the IR-emission intensity compared to the that of the corresponding band for nanorods not doped with the N+ impurity. In the Er-doped nanorods, whose photoluminescence spectra exhibit a high-intensity band at λmax = 1535 nm, the UV emission band at λmax = 372 nm is practically lacking.

Study of thin-film heterostructures produced by laser deposition of a platinum and a lead zirconate titanate layer

We investigate the feasibility of using laser deposition to produce Pt and lead zirconate titanate layers. Optical microscopy, electron microscopy, and atomic-force microscopy of the lead zirconate titanate layer reveal surface roughness on these layers. The optical parameters of the resulting layers were studied by spectral ellipsometry, including the dispersion in the index of refraction and absorption coefficient of the Pt and lead zirconate titanate surface layer. X-ray crystallography indicates that the lead zirconate titanate layer produced has the classical (111) perovskite crystallographic orientation. Similar heterostructures are used as ferroelectric memory elements.

Influence of ion bombardment on residual stresses in diamond-like carbon films

The dependence of internal residual stresses in thin diamond-like carbon films grown by the PECVD technique on the most important growth parameters such as the power of the exciting RF discharge and the substrate bias potential is considered. The results have shown that the mechanical stresses in films reach the uppermost value of 1.9 GPa at the smallest values of power and potential. The stress decreases with the growth of both parameters and has only a slight dependence on the film thickness in the range 0.1–1 μm. The bombardment of the obtained films by argon ions with energy of 300 keV and phosphorus ions with energy of 200 keV has resulted in the reduction of compressive stress with the ion dose growth down to its inversion. AFM study of the bombarded films has revealed significant changes in their surface morphology.

Influence of Silver and Gold Nanoparticles and Thin Layers on Charge Carrier Generation in InGaN/GaN Multiple Quantum Well Structures and Crystalline Zinc Oxide Films

It has been shown that Ag and Au nanoparticles and thin layers influence charge carrier generation in InGaN/GaN multiple quantum well structures and crystalline ZnO films owing to the surface morphology heterogeneity of the semiconductors. When nanoparticles 10 < d < 20 nm in size are applied on InGaN/GaN multiple quantum well structures with surface morphology less nonuniform than that of ZnO films, the radiation intensity has turned out to grow considerably because of a plasmon resonance with the participation of localized plasmons. The application of Ag or Au layers on the surface of the structures strongly attenuates the radiation. When Ag and Au nanoparticles are applied on crystalline ZnO films obtained by rf magnetron sputtering, the radiation intensity in the short-wavelength part of the spectrum increases insignificantly because of their highly heterogeneous surface morphology.