A First-Principles Study Of Nitrogen Vacancy Induced Phase Transition Of Indium Nitride

Narrow band gap semi-conductive nanomaterials are drawing much attention from both industry and academic groups, because it exhibiting excellent usage in many fields, like solar energy, photoelectricity and biomedical science. Indium nitride as one of the most important narrow band gap semi-conductor has been used in solar batteries, laser devices and many others. High quality indium nitride nanomaterials such as nano films and quantum dots could bring better performance for devices, that’s the reason why preparing high quality indium nitride nanomaterials is constantly being an important issue for researchers. Chen Zhuo group has proposed a solution- and vapor-phase method under silica shell confinement, which grow high quality indium nitride quantum dots with uniform spherical shape and cubic zinc-blende phase.Experiments unfold that the phase of indium nitride quantum dots synthesized can be controlled by changing the thickness of silica shell: when the silica shell is relatively thick, which is around 3 to 5 nm, cubic zinc-blende phase is exhibited. And the phase of the product is shifting from pure cubic zinc-blende phase to zinc-blende and wurtzite mixture and finally to pure wurtzite phase when the silica shell is becoming thinner and thinner and finally to none. Actually the coexistence of zinc-blende phase and wurtzite phase is common in synthesis of indium nitride materials. It would be very much meaningful to figure out the mechanism of the coexistence and transformation of these two phases in indium nitride.Pressure is one of the most common factor leading to phase transition. There are a lot of works focusing on pressure induced phase transition in indium nitride as well. Actually, the wurtzite and zinc-blende phase of indium nitride will transit to rocksalt phase under external pressure, however, the wurzite phase will not transit to zinc-blende phase directly under pressure. We expect that the expected phase transition from wurtzite to zinc-blende phase will happen under minus external pressure, but the results suggest that our expectations are not true.The process of the experiment proposed by Chen Zhuo group requires that the reaction must under a certain temperature range, and the temperature is one of the triggers for phase transition. So we made relevant calculations to verify the temperature induced phase transition on indium nitride, however, the verification turns out to be not successful as well.Finally, when we landed on the nitrogen vacancy, which can be result from the nitrogen deficiency in the reaction environment, we got some insight about the whole story of the coexistence and transition of the two phase of indium nitride. The silica shell takes a role of impeding the ammonia molecules to get in, making the environment inside the silica shell nitrogen deficient. Thick silica shell makes more nitrogen vacancies in the indium nitride and forming such nitrogen vacancies in zinc-blende phase is much easier than that in wurtzite phase. That’s why we finally got zinc-blende phase rather than wurtzite phase.This can be an important and direct guidance for growing high quality indium nitride nanomaterials in experiments.