Influence of the thickness on the morphology and sensing ability of thermally-deposited tellurium films

• Published in: Journal of physics. Conference series 2016-03, Vol.700 (1), p.12037
• Main Authors: Hristova-Vasileva, T, Bineva, I, Dinescu, A, Nesheva, D, Arsova, D, Pejova, B
• Format: Article
• Language: English
• Subjects: Ammonia; Atomic force microscopy; Dark current; Ethanol; Evaporation rate; Film thickness; Microscopy; Morphology; Nanorods; Physics; Tellurium; Thick films; Vacuum thermal evaporation
• ISSN: 1742-6588; 1742-6596
• DOI: 10.1088/1742-6596/700/1/012037

Tellurium films with nominal thicknesses of 30, 90 and 300 nm were prepared by thermal evaporation in vacuum at a low deposition rate of 0.3 nm/s. The morphology evolution with the increase of the film thickness was observed by scanning electron microscopy and atomic force microscopy. Nanorods with a width of about 40 nm were observed on the thinnest films surface. On the 90 nm thick films, the formations grew in priority in the z-direction to nanoblades with the same width, but a length of about 100 nm. The further increase of the thickness led to an increase of the 2D nanoobjects' width and length and formation of a stacked nanosheet structure. The surface root-mean-square roughness (Sq) increased with the thickness of the films. Preliminary investigations of the sensing ability of the as-deposited tellurium films with different thicknesses towards water (H2O), ethanol (C2H5OH), acetone (C3H5OH), and ammonia (NH3) vapors were performed by measuring the vapor-induced changes in the film dark current. The films showed appreciable response only to ammonia vapors; their sensitivity was almost equal for the 30 and 90 nm thick films, and decreased significantly for the film tkness of 300 nm.