Proceedings Article | 3 September 2019
Victor Ciupina, Cristian Lungu, Rodica Vladoiu, Gabriel Prodan, Corneliu Porosniccu, Eugeniu Vasile, Madalina Prodan, Virginia Nicolescu, Aurelia Mandes, Virginia Dinca, Ovidiu Cupsa
KEYWORDS: Carbon, Titanium, Multilayers, Silicon, Raman spectroscopy, Diffraction, Resistance, Crystals, Nanostructures
C-Ti multilayer nanostructures were deposed by Thermionic Vacuum Arc (TVA) technology. The layers consisting of about 100nm Carbon base layer and seven 40nm alternatively T i and C layers were deposed on Silicon substrates. The thickness of such a multilayer structure was up to 500nm. On the other hand, in order to obtain C-Ti multilayer structures with variable thickness and different percentages in C and T i of layers, a 20nm thick C layer was first deposed on Si substrate and then seven T i-C layers, each of these having different thickness of up to 40nm were deposed. To perform the successively layers with various thickness were changed the discharge parameters for C and T i plasma sources to obtain the desirable thickness. By changing of substrate temperature between room temperature and 300°C and on the other hand the bias voltage up to −700V , different batches of samples were obtained for this study. To characterize microstructure properties of as prepared C-Ti multilayer structures were used Electron Microscopy techniques (TEM, SEM, STEM), X-Ray Photoelectron Spectroscopy, Raman Spectroscopy and RBS techniques. The measurements reveal the content of diamond-like sp3 and graphite-like sp2 ; the ratio sp3/sp2 increases when the bias voltage increases. Also, HRTEM and SAED patterns reveal an increase of amount and size of TiC nanocrystals with the increase of energy of Ti and C ions determined by increase of anode potential. For providing reliable quantitative information regarding the composition and the elements depth profile, RBS studies were performed using the 3MV Tandem Accelerator with specialized RBS spectrum simulation program SIRMA. Raman measurement reveal that peaks appear at around 250, 340, 420, 610, 740, 1340 and 1530−1567cm−1 , suggesting mixtures of TiC, Ti3C2O2 and Ti3C2 and at 1340, 1560cm−1 , the characteristic D an G peaks of disordered carbon. The characterstic peaks of Ti3C2O2 and Ti3C2 have vibrational modes at 347, 730 and 621cm−1 respectively, peaks at 260 and 420cm−1 correspond to TiC. The shift shown in the spectra of the samples may occurs owing to the mechanical stress. To characterize the electrical conductive properties, the electrical surface resistance versus temperature have been measured, and then the electrical conductivity. Using the Wiedeman-Frantz law was calculated the thermal conductivity, which increase with increase of the temperature, according to the decrease in the proportion of TiC phase.
