Uticaj strukturnih parametara na desorpcione i optičke karakteristike tankih filmova Mg-h i Mg-Ni-H sintetisanih reaktivnim magnetronskim raspršivanjem

Abstract

Doktorska disertacija se bavi istraživanjem uticaja strukturnih parametara tankih filmova Mg-H i Mg-Ni-H na desorpcione i optičke karakteristike filmova sintetisanih reaktivnim magnetronskim raspršivanjem. Analiza tankih filmova bazirana je na praćenju promene optičkih karakteristika koje se javljaju kao posledica promene količine vodonika i samim tim strukture uzoraka. Mg-H filmovi su strukturno modifikovani metodom jonskog bombardovanja, dok su Mg-Ni-H filmovi sintetisani sa narušenim stehiometrijskim odnosom Mg i Ni. Nakon modifikacije Mg-H uzoraka, urađena je analiza kristalne i morfološke strukture upotrebom transmisionog elektronskog mikroskopa (TEM) i objašnjen je uticaj defektne strukture na desorpcione i optičke osobine ovih uzoraka. Termalne metode su korišćene kod analize desorpcionih osobina uzoraka, koje su ujedno ispitivane optičkim mikroskopom spregnutim sa grejnom komorom. Kinetika otpuštanja vodonika ispitivana je JMA jednačinom. Smanjena je temperatura desorpcije modifikovanog uzorka oko 10 °C, a desorpcija je ubrzana 10 puta u odnosu na nemodifikovani uzorak. Uočene promene u boji uzoraka potvrđuju da se desorpcija odvija putem formiranja substehiometrijskih faza MgH2-. Mg-Ni-H filmovi su ispitivani Raderfordovom analizom povratnih jona, metodama rendgenostrukturne analize pod malim uglom i TEM i određena je kristalna i morfološka struktura. Termohromni i fotohromni efekti su potvrđeni u Mg-Ni-H filmu. Desorpcija je promenjena u odnosu na Mg2NiH4, i započinje na nižoj temperaturi. Zaključeno je da se promena u kristalnoj strukturi odražava na desorpciu neaniliranog i aniliranog uzorka, a takođe je dokazano da su desorpcione i optičke karakteristike analiziranih tankih filmova direktno povezane sa postojanjem granicama zrna i defektima u strukturi.

The thesis focuses on investigation of the effect of structural parameters on desorption and optical properties of Mg-H and Mg-Ni-H thin films synthesized by reactive magnetron sputtering. Analysis of thin films was based on changes in optical properties that samples undergo due to a change in amount of hydrogen, followed by structural changes. Mg-H thin films were structurally modified by ion irradiation, while Mg-Ni-H were synthesized aiming a disturbed stoichiometric ratio of Mg and Ni. After modification of Mg-H, analysis of crystallographic and morphological structure was performed using tunneling electron microscope (TEM) and defect structure was related with changes in desorption and optical properties. Thermal analysis was used to investigate desorption properties, which were simultaneously monitored by an optical microscope coupled with a heating stage. Kinetics of hydrogen release was investigated by the JMA equation. Desorption temperature of irradiated Mg-H was reduced by 10 °C and desorption occurs 10 times faster. Observed change in colour confirmed that hydrogen desorption occurs though out a formation of sub-stoichiometric forms of MgH2-. The Mg-Ni-H thin films were investigated by Rutherford backscattering spectrometry, grazing incidence X-ray diffraction and TEM, to determine crystal structure and morphology. Thermochromic and photochromic effects were discovered in Mg-Ni-H. The desorption pathway is changed in comparison to Mg2NiH4 and hydrogen release starts at a lower temperature. It has been concluded that changes in crystal structure affect desorption temperature of as-deposited and annealed samples, and desorption and optical properties of analyzed thin films were related to the presence of grain boundaries and defect structure.