Šarūnas Meškinis

Ion beam synthesis of α-CNx:H films

Hydrogenated amorphous carbon nitride (α-CN x :H) films (100-200 nm) were grown by direct ion beam deposition on Si( 100) substrates. Ion beams have been produced by electrostatic ion sources from C 6 H 14 +H 2 +N 2 gas mixtures. The influence of N 2 / C 6 H 14 +H 2 +N 2 gas ratio (N 2 concentration) on structure and properties of α-CN x :H films was investigated. The increase of N 2 concentration in the gas mixture resulted in decrease of sp 3 bonding and formation of the more graphite-like α-CN x :H films. Growth rate and refractive index of formed α-CN x :H films decreased with increasing N 2 concentration. A slight decrease of wear resistance (<20%) of the formed films with higher nitrogen ratio was also observed.

Fabrication of photonic structures by means of interference lithography and reactive ion etching

Abstract In this study, the fabrication of two-dimensional photonic structures by means of interference lithography is discussed. The proposed method provides flexible formation of various configuration two-dimensional interference patterns depending on the number of beams and their interorientation. Mainly, triangular and square lattice configurations are modeled. It is shown that the dimensions of substructure increase with the number of beams superpositioning. Mask fabrication by SF 6 /N 2 reactive ion etching, while transferring the pattern onto silicon substrate is presented.

Optical properties of the undoped and SiOx doped DLC films

In present study DLC films were deposited by direct ion beam deposition. Hexamethyldisiloxane vapor and hydrogen gas mixture, mixture of the hexamethyldisiloxane with acetylene as well as acetylene gas alone has been used as a source of the hydrocarbons. Optical properties of the synthesized films were investigated by spectroscopic ellipsometry. Structure of the DLC films has been studied by means of the Raman spectroscopy. Effects of the technological deposition parameters such as composition of the gas precursors, ion beam energy, ion beam current density were considered.

The Influence of Annealing on Current–Voltage Characteristics of H2SeO3 Treated Al–nGaAs Schottky Contact

This study the annealing effects on current-voltage and low-frequency noise characteristics of Al-nGaAs Schottky contact were investigated. Selenious acid treatment of GaAs surface prior Al deposition resulted in effective barrier height (φ * b ) reduction up to 0.36 eV and to the Ohmic contact formation after annealing above 450 °C. SEM analysis revealed that Se passivation affected both metallisation morphology and interface reaction kinetic during the Al-GaAs anneals. Observed changes of the Schottky contact barrier height, low-frequency noise and thermostability are explained by the interface Se reactions with both GaAs and Al.

Dynamic optical properties of amorphous diamond-like carbon nanocomposite films doped with Cu and Ag nanoparticles

The investigation of relaxation processes in noble metal nanoparticles upon ultrafast excitations by femtosecond laser pulses is useful to understand the origin and the enhancement mechanism of the nonlinear optical properties for metaldielectric nanocomposites. In the current work we analyze diamond like carbon (DLC) film based copper and silver nanocomposites with different metal content synthesized employing unbalanced magnetron sputtering of metal targets with argon ions in acetylene gas atmosphere. Surface morphology and nanoparticle sizes were analyzed employing scanning electron and atomic force microscopy. Optical properties of the nanocomposite films were analyzed employing UV-VIS-NIR spectrometry. Transient absorption measurements were obtained employing Yb:KGW femtosecond laser spectroscopic system (HARPIA, Light Conversion Ltd.). Energy relaxation dynamics in Cu nanoparticles showed some significant differences from Ag nanoparticles. The increase of excitation intensity hasn’t show additional nonlinear effects for the excited state relaxation dynamics for both kinds of samples.

Electrical properties of the diamond like carbon films irradiated with high energy photons

SiOx—containing amorphous diamond like carbon (DLC) is very attractive material for a number of practical applications. DLC films are possible candidates for the formation of passive layers in electronic devices and are used as protective coatings. Both applications are interesting for the construction of medical radiation detectors. Radiation induced structural changes and electrical properties of DLC: SiOx films (undoped and co-doped) synthesized at room temperature by means of direct ion beam deposition method were investigated after their irradiation with high energy (Emax = 15 MeV) X-ray photons. It was found that transparency of the irradiated DLC films was not changed significantly, as compared to initial samples, stating only small increase of the optical band gap in DLC films. However radiation induced changes were dependent on co-doping and film deposition conditions which were responsible for the sp3/sp2 ratio and hydrogen content in the investigated films. Analysis of U-I characteristics showed decreasing tendency of the leakage current in the range 0–20 V and especially high dependency of breakdown voltage on the deposited contact area in irradiated films as compared to initial samples. Possible mechanism of radiation induced changes in irradiated DLC films is discussed on the basis of the results of Raman and Infrared spectroscopy.

Photovoltaic Properties and Ultrafast Plasmon Relaxation Dynamics of Diamond-Like Carbon Nanocomposite Films with Embedded Ag Nanoparticles

Ultrafast relaxation dynamics of diamond-like carbon (DLC) films with embedded Ag nanoparticles (DLC:Ag) and photovoltaic properties of heterojunctions consisting of DLC:Ag and crystalline silicon (DLC:Ag/Si) were investigated by means of transient absorption (TAS) spectroscopy and photovoltaic measurements. The heterojunctions using both p type and n type silicon were studied. It was found that TAS spectra of DLC:Ag films were dependent on the used excitation wavelength. At wavelengths where Ag nanoparticles absorbed light most intensively, only DLC signal was registered. This result is in good accordance with an increase of the DLC:Ag/Si heterojunction short circuit current and open circuit voltage with the excitation wavelength in the photovoltaic measurements. The dependence of the TAS spectra of DLC:Ag films and photovoltaic properties of DLC:Ag/Si heterostructures on the excitation wavelength was explained as a result of trapping of the photoexcited hot charge carriers in DLC matrix. The negative photovoltaic effect was observed for DLC:Ag/p-Si heterostructures and positive (“conventional”) for DLC:Ag/n-Si ones. It was explained by the excitation of hot plasmonic holes in the Ag nanoparticles embedded into DLC matrix. Some decrease of DLC:Ag/Si heterostructures photovoltage as well as photocurrent with DLC:Ag film thickness was observed, indicating role of the interface in the charge transfer process of photocarriers excited in Ag nanoparticles.

Mechanical Properties of Carbon Thin Films

Thin film — substrate interaction, residual stress and elastic properties in the disperse and films of nanometeric size are of great importance in the development of microsystems, nanostructures and nanomaterials when working with atoms, molecules or supramolecule structures. Scaling down of geometrical dimensions of the structures, devices and systems is accompanied by control of matter on the micro and nano-meter length scale.