Growth without Postannealing of Monoclinic VO2 Thin Film by Atomic Layer Deposition Using VCl4 as Precursor

Abstract

Vanadium dioxide (VO2) is a multifunctional material with semiconductor-to-metal transition (SMT) property. Organic vanadium compounds are usually employed as ALD precursors to grow VO2 films. However, the as-deposited films are reported to have amorphous structure with no significant SMT property, therefore a postannealing process is necessary for converting the amorphous VO2 to crystalline VO2. In this study, an inorganic vanadium tetrachloride (VCl4) is used as an ALD precursor for the first time to grow VO2 films. The VO2 film is directly crystallized and grown on the substrate without any postannealing process. The VO2 film displays significant SMT behavior, which is verified by temperature-dependent Raman spectrometer and four-point-probing system. The results demonstrate that the VCl4 is suitably employed as a new ALD precursor to grow crystallized VO2 films. It can be reasonably imagined that the VCl4 can also be used to grow various directly crystallized vanadium oxides by controlling the ALD-process parameters.

Thermochromic Behavior of VO2/Polymer Nanocomposites for Energy Saving Coatings

“…'Smart' windows are able to intelligently self-regulate the amount of transmitted heat, while keeping the visible transmission mainly unchanged. Vanadium dioxide (VO 2 ) is one of the most promising solid-sate materials for smart windows due to its unique optical properties related to its inherent and ultrafast reversible structural (phase-change) transition from a monoclinic VO 2 (M) to tetragonal rutile VO 2 (R) structure at a critical transition temperature of T C = 68 • C, for pure monocrystalline material [8][9][10].Conventionally, 'smart' thermochromic windows are fabricated by vapor phase deposition techniques such as sputtering [11][12][13][14], chemical vapor deposition (CVD) [15][16][17], and pulsed laser deposition (PLD) [18]. However, all these techniques are restricted by the cost and scale of vacuum systems.…”

“…However, all these techniques are restricted by the cost and scale of vacuum systems. Moreover, most of these growth techniques, although they are of high fidelity and can produce good quality thermochromic VO 2 films, demand high deposition temperatures (>400 • C) [11,[14][15][16][17][18], with very few employing sputtering techniques between 250 and 300 • C [12,13,[19][20][21], making it impossible to utilize flexible (polymeric) substrates.Another approach, called the ex-situ approach [22], to the fabrication of VO 2 thermochromic films is to first synthesize the desired material as a powder and then to deposit the material as a film onto the desired surface. Thermochromic VO 2 in the form of powders have been synthesized by various methods, such as thermolysis [23,24], rapid thermal annealing [25], pyrolysis [26], and, the most utilized method, hydrothermal (solvothermal) synthesis [27][28][29][30][31].…”

“…Conventionally, 'smart' thermochromic windows are fabricated by vapor phase deposition techniques such as sputtering [11][12][13][14], chemical vapor deposition (CVD) [15][16][17], and pulsed laser deposition (PLD) [18]. However, all these techniques are restricted by the cost and scale of vacuum systems.…”

“…However, all these techniques are restricted by the cost and scale of vacuum systems. Moreover, most of these growth techniques, although they are of high fidelity and can produce good quality thermochromic VO 2 films, demand high deposition temperatures (>400 • C) [11,[14][15][16][17][18], with very few employing sputtering techniques between 250 and 300 • C [12,13,[19][20][21], making it impossible to utilize flexible (polymeric) substrates.…”

Photoactive Titanium Dioxide Films with Embedded Gold Nanoparticles for Quantitative Determination of Mercury Traces in Humic Matter-Containing Freshwaters

“…The measured Raman spectrum for the titania films on a silicon wafer support is shown in Figure 4 . The bands located at 301 cm −1 and 520 cm −1 can be assigned to the silicon wafer [ 39 ]. As can be seen, all other Raman bands can be assigned to the anatase phase.…”