Theoretical and experimental characterization of TiO₂ thin films deposited at oblique angles

Abstract

Abstract. The microstructural features of amorphous TiO2 thin films grown by the electron beam physical vapour deposition technique at oblique angles have been experimentally and theoretically studied. The microstructural features of the deposited films were characterized by considering both, the column tilt angle and the increase of the column thickness with height. A Monte Carlo model of the film growth has been developed that takes into account surface shadowing, short-range interaction between the deposition species and the film surface, as well as the angular broadening of the deposition flux when arriving at the substrate. The good match between simulations and experimental results indicates the importance of these factors in the growth and microstructural development of thin films deposited at oblique angles.

Charge collection properties of dye-sensitized solar cells based on 1-dimensional TiO2 porous nanostructures and ionic-liquid electrolytes

“…Deposition was carried out at room temperature and stoichiometric columnar layers of TiO 2 were obtained by performing the evaporation in 10 −4 torrs of O 2 and placing the substrates at a glancing zenithal angle ˛ = 70 • . These glancing geometries produce films with a tilted columnar microstructure [43]. The layer thickness was controlled by monitoring the evaporation process with a quartz crystal monitor previously calibrated by comparing its response with the thickness of several individual films of TiO 2 .…”

“…This geometry leads to the formation of a very open and porous microstructure formed by continuous tilted nanocolumns extending from the substrate up to the surface. The tilting angle of the nanocolumns and the amount of free space in the film can be tuned by controlling the deposition angle ˛ [43]. Zig-zag morphologies can be obtained by turning the substrates around the azimuthal angle (ϕ) during the deposition process [44].…”

“…In this case, results are shown for a series of TiO 2 layers prepared by glancing angle physical vapor deposition (GLAD-PVD) [25,42]. This technique permits a very precise control of the morphology of the nanocolumnar films by playing with the shadowing effects that control the growth during the deposition [43,44]. The TiO 2 layers that can be obtained in this way are characterized by a high porosity [45,46] and relatively large surface areas [25,[47][48][49].…”

Modulating Low Energy Ion Plasma Fluxes for the Growth of Nanoporous Thin Films

“…[16][17][18][19] In contrast with the classical parallel configuration, well known for producing compact layers, the oblique angle geometry promotes shadowing processes of vapor atoms onto the film surface, and facilitates the growth of different tilted nanocolumnar and porous arrays, just like in typical e-beam assisted evaporation at oblique angles. [14,20] However, the presence of a plasma in MS-OAD may introduce further versatility and affect the nanostructural development of the deposited materials. [21] In ref.…”

Enhanced ethanol sensing performance of Fe: TiO2 nanowires and their mechanism of sensing at room temperature

“…TiO 2 and Fe doped TiO 2 thin films were deposited by different methods, such as sol-gel process [9], chemical spray pyrolysis [10,11], sputtering [12], hydrothermal technique [13], reactive pulsed laser deposition [14] and electron beam physical vapour deposition [15]. Among which spray pyrolysis offers a number of advantages over other deposition processes, such as scalability of the process, cost-effectiveness, easiness of doping, operation at moderate temperatures and large uniform surface area.…”