Zn2NF and Related Analogues of ZnO.
Substitution of aliovalent N(3-) and F(-) anions in place of O(2-) in ZnO brings about major changes in the electronic structure and properties, the composition, even with 10 atomic percent or less of the two anions, rendering the material yellow colored with a much smaller band gap. We have examined the variation of band gap of ZnO with progressive substitution of N and F and more importantly prepared Zn2NF which is the composition one obtains ultimately upon complete replacement of O(2-) ions. In this article, we present the results of a first complete study of the crystal and electronic structures as well as of properties of a stable metal nitride fluoride, Zn2NF. This material occurs in two crystal forms, tetragonal and orthorhombic, both with a band gap much smaller than that of ZnO. Electronic structures of Zn2NF as well as ZnO0.2N0.5F0.3 investigated by first-principles calculations show that the valence bands of these are dominated by the N (2p) states lying at the top. Interestingly, the latter is a p-type material, a property that has been anticipated for long time. The calculations predict conduction and valence band edges in Zn2NF to be favorable for water splitting. Zn2NF does indeed exhibit good visible-light-induced hydrogen evolution activity unlike ZnO. The present study demonstrates how aliovalent anion substitution can be employed for tuning band gaps of materials.
New Chemistry Unit, International Centre for Materials Science, CSIR Centre of Excellence in Chemistry, Sheikh Saqr Laboratory, Jawaharlal Nehru Centre for Advanced Scientific Research , Jakkur, Bangalore-560064, India.
Srinivasa Rao
SR
Lingampalli
New Chemistry Unit, International Centre for Materials Science, CSIR Centre of Excellence in Chemistry, Sheikh Saqr Laboratory, Jawaharlal Nehru Centre for Advanced Scientific Research , Jakkur, Bangalore-560064, India.
Krishnappa
K
Manjunath
Theoretical Sciences Unit, Jawaharlal Nehru Centre for Advanced Scientific Research , Jakkur, Bangalore-560064, India.
Sandhya
S
Shenoy
Theoretical Sciences Unit, Jawaharlal Nehru Centre for Advanced Scientific Research , Jakkur, Bangalore-560064, India.
Umesh V
UV
Waghmare
New Chemistry Unit, International Centre for Materials Science, CSIR Centre of Excellence in Chemistry, Sheikh Saqr Laboratory, Jawaharlal Nehru Centre for Advanced Scientific Research , Jakkur, Bangalore-560064, India.
C N R
CN
Rao