xiii, 84 p. ; ill. / This dissertation describes the deposition and characterization of an amorphous thin film with a composition near that of CuInSe 2 (CIS). The creation of an amorphous intermediate leads to a crystalline film at low annealing temperatures. Thin films were deposited from elemental sources in a custom built high vacuum chamber. Copper-selenium and indium-selenium binary layered samples were investigated to identify interfacial reactions that would form undesired binary intermediate compounds resulting in the need for high temperature annealing. Although the indium-selenium system did not form interfacial compounds on deposit, indium crystallized when the indium layer thickness exceeded 15 angstroms, disrupting the continuity of the elemental layers. Copper-selenium elemental layers with a repeat thickness of over 30 angstroms or compositions with less than 63% selenium formed CuSe on deposit. Several deposition schemes were investigated to identify the proper deposition pattern and thicknesses to form the CIS amorphous film. Simple co-deposition resulted in the nucleation of CIS. A simple stacking of the three elements in the older Se-In-Cu at a repeat thickness of 60 angstroms resulted in the nucleation of CuSe and sometimes CIS. The CIS most likely formed due to the disruption of the elemental layers by the growth of the CuSe. Reduction of the repeat thickness to 20 angstroms eliminated the nucleation of CuSe, as predicted by the study of the binary Cu-Se layered samples, but resulted in the nucleation of CIS, similar to the co-deposited samples. To eliminate both the thick Cu-Se region, and prevent the intermixing of all three elements, a more complex deposition pattern was initiated. The copper and selenium repeat thicknesses were reduced into a Se-Cu-Se-Cu-Se pattern followed by deposition of the indium layer at a total repeat thickness of 60 angstroms. At a Se:Cu ratio of 2:1 and the small repeat thickness, no Cu-Se phases nucleated. Additionally, the Cu-In interface was eliminated. For this deposition scheme, films with a selenium rich composition relative to CuInSez were generally amorphous. Those that were Cu-In rich always nucleated CIS on deposit. Annealing of all samples produced crystalline CIS. / Adviser: David C. Johnson

ABSTRACT HYDROGEN STORAGE IN MAGNESIUM BASED THIN FILMS Akyildiz, Hasan Ph.D., Department of Metallurgical and Materials Engineering Supervisor : Prof. Dr. Tayfur &Ouml / zt&uuml / rk Co-Supervisor : Prof. Dr. Macit &Ouml / zenbas October 2010, 146 pages A study was carried out for the production of Mg-based thin films which can absorb and desorb hydrogen near ambient conditions, with fast kinetics. For this purpose, two deposition units were constructed / one high vacuum (HV) and the other ultra high vacuum (UHV) deposition system. The HV system was based on a pyrex bell jar and had two independent evaporation sources. The unit was used to deposit films of Mg, Mg capped with Pd and Au-Pd as well as Mg-Cu both in co-deposited and multilayered form within a thickness range of 0.4 to 1.5 &mu / m. The films were crystalline with columnar grains having some degree of preferred orientation. In terms of hydrogen storage properties, Mg/Pd system yielded the most favorable results. These films could desorb hydrogen at temperatures not greater than 473 K. The study on crystalline thin films has further shown that there is a narrow temperature window for useful hydrogenation of thin films, the upper limit of which is determined by the intermetallic formation. The UHV deposition system had four independent evaporation sources and incorporated substrate cooling by circulating cooled nitrogen gas through the substrate holder. Thin films of Mg-Cu were produced in this unit via co-evaporation technique to provide concentrations of 5, 10 and 15 at. % Cu. The films were 250-300 nm thick, capped with a thin layer of Pd, i.e. 5-25 nm. The deposition was yielded nanocrystalline or amorphous Mg-Cu thin films depending on the substrate temperature. At 298 K, the films were crystalline, the structure being refined with the increase in Cu content. At 223 K, the films were amorphous, except for Mg:Cu=95:5. The hydrogen sorption of the films was followed by resistance measurements, with the samples heated isochronally, initially under hydrogen and then under vacuum. The resistance data have shown that hydrogen sorption behaviour of thin films was improved by size refinement, and further by amorphization. Among the films deposited, amorphous Mg:Cu=85:15 alloy could absorb hydrogen at room temperature and could desorb it at 223 K (50 &ordm / C), with fast kinetics.