Preparation And Field Emission Properties Of Copper Nitride Films By Reactive Radio-frequency Magnetron Sputtering

In recent years, copper nitride (Cu₃N) thin films have attracted considerable attentionfor its distinct structure and low thermal-decomposition temperature. Based on itsunique properties, Cu₃N has potential applications in many fields such as opticalstorage, micro-electronic device and so on. Its low decomposition temperature andnature of non-toxic could be used in write-once-read-many optical storage instead oftellurium.Until now, Cu₃N thin films have been prepared with different methods, includingion-assisted vapor deposition, reactive rf magnetron sputtering, and direct currentsputtering. The method of reactive rf magnetron sputtering with the character ofhighly active and convenient is used most. Focused on the reactive magnetronsputtering preparation and properties of Cu₃N thin films, the main research contents ofthis thesis are shown as follows:1.From XRD patterns, no Cu peaks are found in all the as-deposited films and this indicate that the preferential growth of copper nitride occurs in all films. Also in XRD pattern, a strongest (100) and lower (200), (211) and (220) peaks of the Cu₃N are observed in the film deposited at 0% H₂/N₂ ratios. In the films deposited at 2%～10% H₂/N₂ ratios, the peak of (100) is also the strongest one and a small peak of (111) appears. Although the Cu/N ratios of the films change obviously with the H₂/N₂ ratios, the structure of the films only show very small difference even in the films prepared at 10% H₂/N₂ ratios. This result means that the growth behavior influence by the effect of H₂ on is rather small.2. The effects of H₂/N₂ ratio on the lattice parameter,resistence and optical band gap of Cu₃N films were investigated. The grain size estimated from XRD results is on the order of nanometers. The grain size increases monotonously with increasing H₂/N₂ ratios. The H restricts the nucleation, resulting in the formation of the larger grains. The N content in the Cu₃N films decreases with the increasing H₂/N₂ ratio. The transition of lattice constant is in consistence with the nitrogen content in the films. The optical band gap narrows as the H₂/N₂ ratio increases. this means that the gap of the Cu₃N film could be modulated by H doping. By analysis using TGA in the air, the result shows that the substoichiometrical Cu₃N film with low N content is tended to thermal oxidation at low temperature, and presents poor stability and loses large weight. The resistance of the Cu₃N film decrease when increasing H₂/N₂ ratio. The reason is that Cu atoms transfer to interstitial body-centered position of Cu₃N lattice, and these Cu atoms act as donors. As a conclusion, the Cu₃N films have potential application in microelectronics for its controllable resistance.3. The field emission properties of Cu₃N films with the Cu/N ratio of 3.3:1 are measured with a diode configuration.The field emission shows poor stability, high turn-on electric field and low field emission current. By increasing the H₂ content in the source gas, the Cu content in the film is increased to 80.8 at.%. the field emission properties were improved by showing stability and high emission current, but the turn-on electric field is still high. We consider the increase of Cu content in the film favored the field emission of Cu₃N films.4. The field emission curve of Cu₃N films was analysed using FN,Schottky, SCLC and SCLC+PF models. By mathematical analysis, the correlation coefficients are all very high, proving these models affect the field emission from the Cu₃N films simultaneously, and the I-V relation is the result of these conduction mechanism and FN emission mechanism.