Vanadium oxide thin films
Thin films of vanadium oxide having exceptionally high metal-insulator transition properties are synthesized by RF sputtering. An Al2O3 substrate is placed in a sputtering chamber and heated to a temperature up to about 550 degrees Celsius. Ar and O2 gases are introduced into the sputtering chamber at the flow values of about 92.2 sccm and about 7.8 sccm respectively. A voltage is applied to create a plasma in the chamber. A sputtering gun with vanadium target material is ignited and kept at a power of about 250 W. The phase transition parameters of vanadium dioxide thin films, synthesized by RF sputtering, are modulated by exposing the vanadium dioxide thin film to UV (ultraviolet) radiation so as to induce a change in oxygen incorporation of the vanadium dioxide thin film.
1. A method comprising:
placing a substrate in a sputtering chamber and heating the substrate prior to sputtering;
placing a VO 2 target material in a sputtering gun inside the sputtering chamber, the target material including a crystalline oxide;
introducing into the sputtering chamber an inert gas at a first flow rate, then a reactive gas at a second flow rate;
applying a voltage within the sputtering chamber to create a plasma within the sputtering chamber;
activating the sputtering gun at a distance from the substrate so as to cause the crystalline oxide in the target material to react with the reactive gas, and so as to cause a layer of a compound of the reactive gas and the crystalline oxide to be deposited on the substrate, thereby creating a single stoichiometric phase, polycrystalline VO 2 thin film;
keeping the substrate at a temperature between 300° C. and 550° C. during sputtering, and cooling down the deposited VO 2 thin film to a temperature of about 150° C. after the deposition;
wherein the first flow rate is 29 sccm and the second flow rate is 7.8 sccm, so that the ratio of vanadium to oxygen in the thin film allows the thin film to undergo a metal-insulator transition (MIT) of four orders of magnitude in resistance at an MIT temperature between 61° C. and 71° C.
2. The method of claim 1 , wherein the target material comprises vanadium dioxide.
3. The method of claim 1 , wherein the target material comprises vanadium.
4. The method of claim 1 , wherein the substrate is at least one of: a S i /S i O 2 substrate; and an Al 2 O 3 substrate.
5. The method of claim 1 , wherein the inert gas is Ar.
6. The method of claim 1 , wherein the reactive gas is O 2 .
7. The method of claim 1 , further comprising the act of maintaining the sputtering gun at a power of about 250 W.
8. The method of claim 1 , wherein the distance from the substrate is about 6 inches.
9. The method of claim 1 , wherein the sputtering chamber has a base pressure of between about 2×e-08 Torr to about 3×e-08 Torr.