Sputtered Tungsten Oxide Research Articles

Preparation and properties of reactively sputtered tungsten oxide films: H Kaneko et al, J Appl Phys, 53 (4), 1982, 3070–3075

Preparation and properties of reactively sputtered tungsten oxide films: H Kaneko et al, J Appl Phys, 53 (4), 1982, 3070–3075

Preparation and properties of reactively sputtered tungsten oxide films

Properties of reactively sputtered tungsten oxide films for electrochromic display devices have been investigated. The films (2000–23000 Å thick) were formed by rf sputtering from a metallic tungsten target under a constant operating pressure ranging from 5×10−3 to 6×10−2 Torr using a mixture of Ar-4–50% O2. Electrical resistivity of the films formed increases remarkably with increasing oxygen concentration and total operating pressure of the sputtering atmosphere, ranging from 10−3 to 1011 Ω⋅cm. The films 5900–9200 Å thick prepared in a sputtering atmosphere of Ar-10% O2 under a constant operating pressure higher than 2×10−2 Torr are transparent and have a spectral transmittance of about 85% in the visible and infrared region. Optical band gap and refractive index of these films are 3.01–3.08 eV, and 2.2–2.4, respectively. Electrochemichromic properties of the films were also studied using asymmetric cells, and it was found that a good electrochromic performance was achieved usually by the cells composed of the transparent films with a resistivity of 106–1010 Ω⋅cm.

Electrical and optical properties of reactively sputtered tungsten oxide films

Electrical and optical properties of reactively sputtered tungsten oxide films have been investigated in relation to the oxygen concentration in sputtering atmosphere. The films with 5200–6600 Å thick were prepared under a constant pressure of 5×10−3 Torr using a mixture of Ar and 4–50% O2. Electrical resistivity and spectral transmittance of the films formed depend extremely on the oxygen concentration in the atmosphere. The films formed in an atmosphere containing less than 13% O2 are semiconductive, have a resistivity of 10−3–103 Ω cm, and are blue colored. The films formed in an atmosphere containing more than 16% O2 are transparent and have a resistivity of 107–1011 Ω cm. Optical band gap of the films formed under a sputtering atmosphere containing 8–50% O2 is almost constant and ranges 3.00–3.03 eV. The carrier concentration and Hall mobility of semiconductive films and the refractive index of insulating films were also measured. The presence of a critical oxygen concentration for the formation of either semiconductive or insulating films has been suggested.