Effect of hot-filament annealing in a hydrogen atmosphere on the electrical and structural properties of Nb-doped TiO 2 sputtered thin films

• Type: Article in International Scientific Journal
• Date: 2012

Authors

C. J. Tavares (Author) Other; M. V. Castro (Author) Other; E. S. Marins (Author) Other; A. P. Samantilleke (Author) Other; S. Ferdov (Author) Other; L. Rebouta (Author) Other; M. Benelmekki (Author) Other; M. F. Cerqueira (Author) Other; P. Alpuim (Author) Other; E. Xuriguera (Author) Other; J. P. Rivière (Author) Other; D. Eyidi (Author) Other; M. F. Beaufort (Author) Other; A. Mendes (Author) FEUP

Journal

Title: Thin Solid Films

Vol. 520 No. 7

Pages: 2514-2519

ISSN: 0040-6090

Publisher: Elsevier

Indexing

ISI Web of Knowledge - 13 Citations

ISI Web of Science

Scopus - 16 Citations

INSPEC

Scientific classification

FOS: Engineering and technology > Chemical engineering

Associated Projects

PEst-C/EQB/UI0511/2011 - PROJECTO ESTRATÉGICO - UI 511 - 2011-2012

Other information

Authenticus ID: P-002-DSQ

DOI: 10.1016/j.tsf.2011.10.031

Abstract (EN): In this work Nb-doped TiO2 thin films were deposited by d.c.-pulsed reactive magnetron sputtering at 500 °C from a composite target with weight fractions of 96% Ti and 4% Nb, using oxygen as reactive gas. In order to enhance the conductive properties, the as-deposited samples were treated in vacuum with atomic hydrogen at a substrate temperature of 500 °C. The atomic hydrogen flow was generated by a hot filament, inside a high-vacuum chemical vapour deposition reactor, at a temperature of 1750 °C. In order to optimise the hydrogen hot-wire treatments, the H2 pressure was varied between 1.3 and 67 Pa, the treatment time was monitored between 1 and 5 min and the hot-filament current was changed between 12 and 17 A. Dark conductivity was measured as a function of temperature and its value at room temperature was extrapolated and used to assess the effect of the hydrogen annealing on the charge transport properties. A two-order of magnitude increase in dark conductivity was typically observed for optimised hydrogen treatments (10 Pa), when varying the hydrogen pressure, resulting in a minimum resistivity of ~3× 10¿3 ¿ cm at room temperature. The maximum amount of atomic H incorporation in oxygen vacancies was determined to be ~5.7 at.%. Carrier mobility and resistivity were also investigated using Hall effect measurements. Correlations between structural and electrical properties and the hydrogen treatment conditions are discussed. The purpose of these films is to provide a transparent and conductive front contact layer for a-Si based photovoltaics, with a refractive index that better matches that of single and tandem solar cell structures. This can be achieved by an appropriate incorporation of a very small amount of cationic doping (Nb5+) into the titanium dioxide lattice.

Language: English

Type (Professor's evaluation): Scientific

Notes: Publicação abrangida pelo Journal Citation Reports 2015

No. of pages: 6