Real-time measurement of oxidation dynamics of sub-stoichiometric tungsten oxide films by pulsed laser deposition

Abstract

In this study WO x films were deposited by laser ablation of ultra-pure (5N) tungsten trioxide targets onto SiO 2 or silicon substrates at 250°C temperature, 100 mTorr oxygen partial pressure and 1 × 10 −5 Torr vacuum. Surface chemical states and compositions of the deposits were determined by X-ray photoelectron spectroscopy. The results showed that deposits in oxygen partial pressure contain W 6+ with x ∼ 3.1, while vacuum-deposited films have different W states with various percentage distributions as W 4+ > W 5+ > W 6+ > W 0 , and x ∼ 1. We used fast electrical resistance measurement as a probe to study the deposition process. Film resistance as a function of deposition time in vacuum revealed some microsecond fluctuations modulated on the time variation curve of electrical resistance. We attribute these data to surface absorption and desorption of oxygen during layer deposition. Finally, the effect of the laser beam on the target's structure, surface morphology and chemical state was studied. Our results revealed that in spite of structural variation by laser irradiation, the O/W ratio remained about 3.

pH-Dependent Assembly of Tungsten Oxide Three-Dimensional Architectures and Their Application in Photocatalysis

“…Figure S1 (Supporting Information) shows the W 4f core level spectrum of WO 3 prepared at different pH values. From the fitted peaks of W 4f, two main peaks were separated at 35.7 eV (W 4f 7/2 ) and 37.8 eV (W 4f 5/2 ), 26 which are indicative of W 6+ . For all the samples, the valence states of W are +6 and no evidence of the W 5+ state was found.…”

Electroless plating of palladium on WO3 films for gasochromic applications

“…In this study the PLD technique for WO 3 together with electroless plating for Pd was employed. PLD technique is a successful fabrication method of compound films such as metal oxides [11,12]. It can also be accompanied with O 2 partial pressure to retain the stoichiometry of films.…”

Photoelectrochemical study of MoO 3 assorted morphology films formed by thermal evaporation

“…Molybdenum oxide (MoO 3 ) is one of the very important types of semiconducting materials which possess excellent electrochromic, optochromic, and gasochromic properties [11][12][13][14][15] . In the past, MoO 3 has been used to manufacture various devices such as flat-panel displays, electrochromic smart windows, optical modulation devices, write-read-erase optical devices, sensors and field emission devices [16][17][18][19][20][21] . To date, molybdenum oxide is the benchmark semiconductor for PEC application due to its chemical stability and high activity.…”