Sapphire substrates with a regular surface relief
- PDF / 1,176,063 Bytes
- 4 Pages / 612 x 792 pts (letter) Page_size
- 83 Downloads / 177 Views
ACE AND THIN FILMS
Sapphire Substrates with a Regular Surface Relief A. V. Butashina, V. M. Kanevskya, A. E. Muslimova, A. L. Vasilyevb, Yu. N. Emirovc, E. V. Rakovaa, A. S. Golubevaa, and A. M. Klevacheva a
Shubnikov Institute of Crystallography, Russian Academy of Sciences, Leninskii pr. 59, Moscow, 117333 Russia email: [email protected] b National Research Centre “Kurchatov Institute”, pl. Akademika Kurchatova, Moscow, 123182 Russia c Florida International University, 11200 SW 8th St, Miami, FL 33174 Received April 7, 2014
Abstract—The lithographyfree technique is proposed to obtain a regular relief in the form of a regular 2D system of 25nm protrusions on a sapphire plate surface. The use of grid masks allows one to form a regular relief on the sapphire substrates of arbitrary area. The structure of crystal films formed by the sputtering of metal aluminum onto sapphire substrates with subsequent oxidation and annealing is thoroughly investigated and compared with the nanostructured (0001) sapphire wafer surface in the form of regular steps up to 5 nm in height with atomically smooth terraces. DOI: 10.1134/S1063774514050022
1. INTRODUCTION
EXPERIMENTAL
It was found during the development of epitaxial technology that the use of sapphire substrates with a regular surface micro and nanorelief instead of the substrates with an ultrasmooth surface may noticeably improve the structural quality of the semiconductor crystal films grown on them [1–6]. In nanotechnolo gies, such substrates are used to form ordered ensem bles of metal nanoparticles, semiconductor nanow ires, and carbon nanotubes [7–9].
Substrates about 20 mm in diameter were cut from standard sapphire wafers (Shubnikov Institute of Crys tallography, Russian Academy of Sciences) with one side treated by chemical mechanical polishing to obtain an average roughness of no more than 0.3 nm. The substrate surface made angles from 0.1° and 3° with the (0001) crystallographic plane The regular microrelief on the sapphire substrate surface was formed by the vacuum sputtering of metal lic aluminum trough masks with (0.2–40)µm holes (metal grids and polymer films with holes, socalled nuclear filters) and subsequent annealing in air at 1400°С for 1 h. The protrusion height was limited to 50 nm to avoid the formation of caverns at the Al2O3 film/ Al2O3 sub strate interface, which was observed in [12] upon the oxidation of aluminum films with thicknesses of 100– 1000 nm on the sapphire substrate. To recrystallize the substrate surface and form a step nanostructure with terraces from the atomically smooth (0001) faces on it, the samples were annealed in air or vacuum at a temperature of 1000°С or more [11]. The phase composition and orientation of crystal films were determined by reflection highenergy (Е = 75 keV) electron diffraction. The surface morphology of the sapphire substrates and grown films was studied in the topography mode on an Ntegra Aura atomic force microscope (NTMDT, Zelenograd). The crystal structure of the Al2O3 layers forming a regu
Data Loading...
