Doping Alkali Atom Effectively Improving The Electronic And Nonlinear Optical Properties Of Inorganic AlN Nanocage

Due to the high thermal stability and chemical stability, inorganic aluminumnitride (AlN) nano-materials possess very broad application prospects, andconsequently get the favor of people. As an important member of the AlN family, AlNnanocages also attract extensive attention of the researchers. However, inorganic AlNnanocages usually possess the wide HOMO-LUMO gap, hindering their potentialapplications in the field of nanoscale electronic devices, etc. In order to break throughthe bottleneck, based on the quantum chemical methods-ab initio in theory, this thesistakes the Al12N12cage as a representative which is the most stable nanostructure in thefamily of inorganic AlN nanocage, to investigate that doping the alkali atoms cansignificantly improve the electronic and NLO properties of AlN nanocage, the maincontributions are as followings:1、The alkali atoms can steadily adsorb on the surface of inorganic AlN nanocage,and their corresponding binding energies (Eb) are in the range of11.7~33.5kcal/mol,much larger than10kcal/mol. Obviously, all of these new electrides M@x-Al12N12(M=Li, Na and K; x=b66, b64and r6) can exhibit considerable structural stability.2、Doping the alkali atom can significantly narrow the wide HOMO-LUMO gap(EH-L=6.12eV) of pure Al12N12nanocage in the range of0.49~0.71eV and thesedoped AlN nanocages can exhibit the intriguing n-type characteristic. It is thus clearthat doping alkali atoms can effectively break through the bottleneck of wideHOMO-LUMO gap in the inorganic AlN nanocage, promoting their practicalapplications in the future AlN-based nanoscale electronic devices.3、The diffuse excess electron produced by alkali atoms interacting with theAl12N12nanocage can significantly enhance the nonlinear optical response (NLO) ofthe doped systems. The first hyperpolarizabilities (β0) of these new formed electrides are1.09×104au for Li@b66-Al12N12,1.10×104,1.62×104,7.58×104au forM@b64-Al12N12(M=Li, Na and K), and8.89×105,1.36×105,5.48×104au forM@r6-Al12N12(M=Li, Na and K), respectively. Moreover, we find that the alkaliatomic number and doping position can affect the β0values of the doped systems: theβ0values of M@b64-Al12N12monotonically increase with increasing the alkali atomicnumber, where the alkali atoms is located over the Al-N bond of Al12N12cage; the β0values of M@r6-Al12N12monotonically decrease with increasing the alkali atomicnumber, where the alkali atoms is located over the r6ring of Al12N12cage.The results will be advantageous for promoting the extensive applications of theinorganic AlN-based nano-materials in the field of multi-functional nanoscaleelectronic nanodevices and the design of new type of high-performance NLOmaterials, etc.