Loading...
2 results
Search Results
Now showing 1 - 2 of 2
- Influence of growth temperature and carrier flux on the structure and transport properties of highly oriented CrO2 on Al2O3 (0001)Publication . Sousa, Pedro M.; Dias, Sonia A.; Conde, Olinda; Silvestre, António Jorge; Branford, William R.; Morris, Benjamin; Yates, Karen; Cohen, Lesley F.In this work we report on the structure and magnetic and electrical transport properties of CrO2 films deposited onto (0001) sapphire by atmospheric pressure (AP)CVD from a CrO3 precursor. Films are grown within a broad range of deposition temperatures, from 320 to 410 degrees C, and oxygen carrier gas flow rates of 50-500 seem, showing that it is viable to grow highly oriented a-axis CrO2 films at temperatures as low as 330 degrees C i.e., 60-70 degrees C lower than is reported in published data for the same chemical system. Depending on the experimental conditions, growth kinetic regimes dominated either by surface reaction or by mass-transport mechanisms are identified. The growth of a Cr2O3 interfacial layer as an intrinsic feature of the deposition process is studied and discussed. Films synthesized at 330 degrees C keep the same high quality magnetic and transport properties as those deposited at higher temperatures.
- Co and (Co,Mo) doping effects on the properties of highly reduced TiO2 anatase thin filmsPublication . Silvestre, António Jorge; Rout, S.; Dalui, S.; Pereira, Laura; Viana, Ana; Conde, OlindaThis work reports on the structural, optical, electrical and magnetic properties of Co:TiO2 and (Co,Mo):TiO2 anatase thin films grown onto (0001) sapphire substrates by Pulsed Laser Deposition in highly reducing conditions and at a low temperature of 350 _C. Undoped TiO2_d as well as doped films with nominal compositions of Ti0.95Co0.05O2_d, Ti0.94Co0.05Mo0.01O2_d, and Ti0.92Co0.05Mo0.03O2_d were studied. They all show similar microstructures, with smooth surfaces and RMS roughness values less than 0.5 nm. The optical band gap energies of the doped films are red shifted with respect to that deduced for the undoped TiO2_d. The correlation between the band gaps and the Urbach energies of the films is discussed. All samples show semiconductor behavior with n-type conduction. The Co:TiO2 sample is ferromagnetic with a saturation magnetization of 1.3 mB/Co, a high electrical conductivity of 123 S cm_1 and a carrier density of 1.88 _ 1021 cm_3 at room temperature. The ferromagnetic order of the Co:TiO2 system is suppressed when carriers are added by codoping with Mo.