Metal–insulator transition characteristics of Mo- and Mn-doped VO₂films fabricated by magnetron cosputtering technique

Abstract

Mo-and Mn-doped VO 2 thin films have been grown on c-cut sapphire substrates by the magnetron co-sputtering technique. The effects of Mo and Mn doping on the structure and metal-insulator transition of the doped VO 2 thin films were studied. An enlargement of the out-of-plane lattice constant of the film caused by Mo doping was observed. As expected, the transition temperature (T MI) is reduced by Mo doping. However, the valence of the Mo ions doped in the VO 2 films is determined by X-ray photoelectron spectroscopy to be 6+ on the surface, but 4+ and 3+ in the bulk part of the films. The reduction in T MI observed in this study is attributed to the variation in the band structure resulting from the incorporation of Mo 4+ into the VO 2 lattice. The optical transmission is remarkably enhanced by low-concentration Mo doping and then monotonically decreases with increasing Mo content. On the other hand, the out-of-plane lattice constant and T MI are not affected by Mn doping. The transmission is enhanced and then monotonically increases with increasing Mn concentration. The thermochromism of doped films is suppressed by Mo and Mn doping.

Nanocolumnar Crystalline Vanadium Oxide-Molybdenum Oxide Antireflective Smart Thin Films with Superior Nanomechanical Properties

“…The data presented in Fig. 2(c) confirmed the presence of crystalline phases of mixed vanadium oxide of different oxidation state915202438 e.g., V 2 O 5 , V 2 O 3 and VO 2 and molybdenum oxide. The patterns exhibited eleven peaks in the 2θ range of 10–70° corresponding to the VO 2 : ICSD-199, V 2 O 5 : ICSD-43132, V 2 O 3 : ICSD-655262 and MoO 3 : ICSD-152313.…”

“…Among all the aforesaid oxides, VO 2 and V 2 O 5 are extensively investigated owing to the passion of positive phase transition temperatures. The tuning of transition temperature of vanadium oxide is usually achieved by doping/adding second phase with other transition metals e.g., both higher and lower valent metals such as Mo14151617181920212223242526, W27, Mn15, Ti2829, Nb2630, Cr30 and noble metal i.e., Au31 as well. After doping/adding second phase, the transition temperature of vanadium oxide is reported to be decreased141517181920242531.…”

“…The Mo and/or molybdenum oxide doped vanadium oxides are reported to be grown by a multitude of techniques such as magnetron sputtering technique15, atmospheric pressure chemical vapour deposition26, cathodic elctrodeposition16, sol-gel1417202124, hydrothermal synthesis1921, combustion synthesis technique18, spray pyrolysis25 and electron beam evaporation techniques2223. In general, the introduction of Mo or oxides of Mo are reported to have assisted in various extents of reduction in the transition temperature of VO 2 e.g., from about 68 °C32 to 55–30 °C1724, 50 °C25, 53–(−)91 °C15, 47.5–24 °C14 and 25 °C19.…”

“…In general, the introduction of Mo or oxides of Mo are reported to have assisted in various extents of reduction in the transition temperature of VO 2 e.g., from about 68 °C32 to 55–30 °C1724, 50 °C25, 53–(−)91 °C15, 47.5–24 °C14 and 25 °C19. The optical properties such as transmittance15162122232425, reflectance14 and electrical conductivity of these coatings are also extensively studied14151820212223. For instance, the electrochromic behaviour is investigated by Jin et al 16.…”

“…For instance, the electrochromic behaviour is investigated by Jin et al 16. Additional efforts are also directed towards the dissociation1415171820 induced reduction of the V 2 O 5 phase as well as enhancement in crystallinity15 through vacuum annealing at high temperature e.g., 450–500 °C. There is only a lone attempt33 to reduce the vacuum annealing temperature of pure i.e., un-doped vanadium oxide system further downwards to e.g., 200–500 °C.…”