1% La doped BaSnO3 thin films of different thicknesses, ranging from 15 to 300 nm, were obtained on single crystal Lanthanum Aluminate-Strontium Aluminate Tantalate [LSAT(001)] substrates via Pulsed Laser Deposition. The films grow epitaxially on these substrates (cube-on-cube epitaxy) and are almost relaxed with a strain of ≈0.51% for 300 nm films. All films show n-type conducting behavior with their conductivity varying from 65.36 S cm−1 to 465.11 S cm−1 as the thickness of the film is increased. Low temperature carrier concentration measurements indicate that the films are degenerate semiconductors. Films with a thickness ≥30 nm exhibit metal to semiconductor transition (MST) at low temperatures. Temperature dependent resistivity analysis of the films shows evidence of electron-electron interaction rather than weak localization as the governing transport mechanism below MST. The transition temperature shifts toward lower values at higher thicknesses, strengthening the metallic transport in such films.

The nucleation and growth mechanism of functional oxides have a direct bearing on the structural and electronic properties of the deposit. We study the effect of electrolyte pH and deposition potential on the nucleation and growth of Cu2O on polycrystalline metal oxide (FTO) & metal (Au) substrates. Modelling of the recorded current-time transients indicates that both instantaneous and progressive nucleation occur with growth limited by diffusion or lattice incorporation of electro-active species or both. The preferred orientation of Cu2O shows strong dependence on electrolyte pH. The films are (100) oriented on both substrates at pH 9 except at high applied potential on FTO where the orientation changes to (111). Interestingly, irrelevant of electrolyte pH, the grain size of Cu2O decreases with potential on FTO whereas it increases on Au substrates. We attribute this to a difference in the number of active nucleation sites between the two substrates. The nucleation and growth at pH 12 is observed to be dependent both on diffusion and lattice incorporation of electro-active species. Additionally, the films are primarily (111) oriented on both the substrates, which is correlated to the availability of OH– ions.

Lowering the synthesis temperature to obtain phase pure BaSnO3, which is the host material for high figure-of-merit (FOM) perovskite transparent conductors (TCs), can expand the horizons for its optoelectronic applications, with an obvious reduction in the thermal budget. In this work, we have developed a novel solution combustion technique for the synthesis of BaSnO3 nanoparticles. A peroxo/superoxo precursor to the nanoparticles is first synthesized by co-precipitation of the tin and barium salts via the H2O2 assisted or the `CSMC' route. The phase evolution, under different drying conditions of the wet precursor to crystalline BaSnO3 nanoparticles is then studied. We find that the crystallization temperature of BaSnO3 is significantly reduced by adding an organic solvent such as ethanol or propanol to the precursor; temperatures as low as 130 °C yield phase pure BaSnO3 nanoparticles. We establish that the organic solvent increases the reactive O2 ligand content, which plays a pivotal role in the synthesis. Due to this, an exothermic reaction occurs around 130 °C, thereby providing the heat of reaction for conversion of the precursor to phase-pure BaSnO3. Importantly, this method should also allow for the facile incorporation of dopants, paving the way for synthesis of high FOM TCs at low temperatures. Such low synthesis temperatures enable BaSnO3 to be used in devices having temperature limitations during device processing, such as heterojunction Si solar cells or perovskite-based solar cells in an n-i-p architecture.