Zhi-Hao Jin

Morphological properties of AlN piezoelectric thin films deposited by DC reactive magnetron sputtering

Abstract This paper deals with the formation of AlN thin films successfully deposited on Si(111) substrates by using the direct current magnetron sputtering method. The films feature planes with (100) and (002) preferential orientations, low surface roughness and a homogeneous composition. The effects of the sputtering pressure, sputtering power and distance ( D ) from the target to the substrate on the preferential orientation of the AlN films are also studied. The results show that a lower sputtering pressure and shorter distance D are conducive to the formation of the (002) plane. On the contrary, a higher sputtering pressure and longer distance D are beneficial for the growth of the (100) plane. Moreover, the preferential orientation of the AlN thin film is also dealt with from the viewpoint of the formation of the AlN chemical bond and the mean free path of sputtered particles.

Ab initio calculation of SiC polytypes

Abstract A systematic study of ground-state property of cubic and hexagonal silicon carbide polytypes (3C-, 6H-, 4H-, and 2H–SiC) is reported using the ultrasoft and norm-conserving pseudopotential methods of density-functional theory in the local-density approximation. The electronic and geometry structures of SiC polytypes are discussed in comparison with the experimental data. The conduction-band minimum with ultrasoft pseudopotential is the closest to (0.0,0.5,0.0) point as energy band calculation with several pseudopotentials. There is a marked discontinuity along ML line in the Brillouin zone with norm-conserving pseudopotential proposed by Lin. Both energy gap and valence-band width for the structure optimized with ultrasoft pseudopotential are greater than that with Lin’s. pseudopotential.

Structure and stability of SinCm−n clusters

Abstract In this paper, both ab initio and density functional theory methods have been used to predict geometries, electronic states and energies of Si n C m − n ( n =1,2; m =3–16). Harmonic frequencies for these clusters are given in order to aid in the characterization of the ground states. These results show that SiC m −1 ( m =3–9) clusters form linear structure and SiC m −1 ( m =10–16) isomers form ring structure. Si 2 C m −2 ( m =4–16) clusters have linear structure except ring isomer of Si 2 C 12 molecule. Si atom favor to bond at end in linear isomers. However, C atom themselves favor to bond in the cyclic isomers. The stability of the Si n C m − n ( n =1,2; m =3–16) clusters with odd m are greater than that with even m .

First principles study of the structure, electronic state and stability of SinC−m anions

Abstract Structure, electronic state and energy of SinC− and SinC−2 (n=1–7) anions have been investigated using the density functional theory. Structural optimization and frequency analysis are performed at the level B3LYP/6-311G(d). The charged-induced structural changes in these anions have been discussed. The strong C–C bond is also favored over C–Si bonds in the SinC−m anions in comparison with corresponding neutral cluster. Among different SinC− and SinC−2 (n=1–7) anions, Si 3 C − , Si 5 C − and Si2C−2 are most stable. Their stability has a decreasing tendency with the increase in the size of these clusters.

First principles studies on the structures, electronic states and stability of SinCm+ cationic clusters

Abstract Geometries, electronic states and energies of Si n C + and Si n C 2 + ( n =1–7) have been investigated using the density functional theory. Structural optimization and frequency analyses are performed with the basis set of 6-311G(d). The calculations predict the existence of a number of previously unknown isomers. The strong C–C bonds are favored over C–Si bonds in the Si n C 2 + cationic species. The Si 3 C + , Si 5 C + , Si 2 C 2 + and Si 3 C 2 + are more stable in the Si n C + and Si n C 2 + ( n =1–7) cationic isomers.

ClAlNH)n cluster formation in the gas phase for the chemical vapor deposition of AlN thin films

Abstract In this paper, both ab initio and density functional theory methods have been used to predict geometries, electronic states and total energies of (ClAlNH)n (n=1–10) clusters. Harmonic vibrational frequencies for these clusters are given in order to aid in the characterization of the ground states. In addition, the thermodynamic properties of the oligomerization processes (ClAlNH)m→m/n(ClAlNH)n are discussed in detail. These results show that the ground state geometric structures of (ClAlNH)n(n=1–10) clusters are Cs(n=1), D2h(v=2), D3h(n=3), Td(n=4), Cs(n=5), D3d(n=6), Cs(n=7), S4(n=8), D3h(n=9) and C2hn=10) symmetry, respectively. The stabilities of the (ClAlNH)n clusters with even n (n=2, 4, 6, 8, 10) are greater than that with odd n (n=1, 3, 5, 7, 9).

Ab initio studies on the structures, adiabatic ionization potentials and stability of SiCm−1+ clusters

Abstract Structural and electronic properties of semiconductor binary SiC m −1 + ( m =3–16) clusters have been investigated using the B3LYP-DFT method. Full structural optimization and the adiabatic ionization potential calculation are performed with the basis of 6-311G ∗ . These results show that SiC m −1 + ( m =3–10) isomers have chained structures and SiC m −1 + ( m =11–16) species have ring structures. Si atom favor to bond at end in chained isomers whereas C atoms themselves favor to bond in the cyclic structures. The stability of the SiC m −1 + ( m =3–16) clusters with odd m are greater than that with even m . The relative stability becomes more and more weak.