First-principles study on the diffusion dynamics of Al atoms on Si surface

Abstract

<sec>Density functional theory is used to calculate the adsorption and diffusion behavior of Al atoms on clean, H-terminate, Cl-terminate Si(100) and Si(111) surfaces. The most stable position of Al atom adsorption and the diffusion path are different on Si(100) surface terminated by different methods. On the surface of clean Si(100), the <i>Tr</i> site is the most stable site for Al atom with an adsorption energy of 4.01 eV, and the <i>H</i> and <i>M</i> sites are the sub-stable stable sites with the adsorption energies of 3.51 eV, and 3.63 eV, respectively. When the Al atom is adsorbed at the <i>Tr</i> site on the clean Si(100) surface, it bonds with the Si atom to destroy the Si—Si bond in the dimer. Therefore Al is easily adsorbed at the <i>Tr</i> site of the trench and diffuses in a zigzag pattern along the trench. On the H-terminate and Cl-terminate Si(100) surface, Si—Si bonds in the dimer column are changed from cross to parallel. Al is easily adsorbed at the <i>H</i> position at the top of the dimer column, and diffuses along the line at the top of the dimer. The differential charge density shows that the Al atom transfers electrons to the Si atoms on the surface, and the surface H-terminate and Cl-terminate weaken the interaction between Al atoms and Si, and reduces the diffusion energy barrier of Al atoms. </sec><sec>The Si(111) surface terminated by different methods has the same stable position (<i>T</i><sub>4</sub> site) for the adsorption of Al atoms. When Al atom adsorbs at the <i>T</i><sub>4</sub> site on the clean Si(100) surface, it bonds to Si atom, which located at the three <i>T</i><sub>1</sub> site, then Al atom is firmly fixed by the three Al—Si bonds with a bond length of 2.55 Å. Thus Al atom can has the largest adsorption energy and form the most stable state at the <i>T</i><sub>1</sub> site. With the diffusion and migration of Al atom, the bond between Al atom and the <i>T</i><sub>1</sub> site in the opposite direction appears to be broken. When Al atom migrating to the saddle point position is the most unstable. Here Al atom bonds to the Si atoms of the two adjacent <i>T</i><sub>1</sub> sites to form a bond with a length of 2.49 Å, which is 0.06 Å shorter than the initial Al—Si bond (2.55 Å). What’s more, the diffusion energy barrier of Al atom at this position is 0.65 eV, which impede Al atom to diffuse and migrate. When Al atom migrates to the <i>H</i> site, it rebonds to the three Si atoms on the adjacent surface and forms a bond with a length of 2.52 Å, which is 0.03 Å shorter than the Al—Si bond (2.55 Å) at the initial position. On the H-terminate and Cl-terminate Si(111) surface, Al atom doesn’t bond with Si atom for the H or Cl saturates the dangling bonds on the Si surface. The Si(111) surface terminated by different methods has the same stable position for adsorption of Al atoms. The diffusion paths of Al atoms are similar, and they are easy to be adsorbed to the top position (<i>T</i><sub>4</sub> site) of the second Si atom, and the path along <i>T</i><sub>4</sub> to <i>H</i><sub>3</sub> is diffused. Similarly, the H-terminate or Cl-terminate of Si(111) surface weakens the electron transfer between Al and Si atoms and reduces the diffusion energy barrier of Al atoms. Regardless of the Si(100) or Si(111) surface, the H-terminate and Cl-terminate Si surfaces are effective in reducing the diffusion barrier of Al atoms.</sec>

Deposition behavior and mechanism of thermal sprayed SiC

“…As shown in Figure 9D, the lattice fringes of area‐2 displayed interplanar spacings of 0.197 and 0.190 nm, which matched well with those of the (2 2 1) and the (0 4 0) planes of the orthorhombic mullite. Combined with the oxidation phenomenon of the collected spray powder, it is the fused SiO 2 and the decomposed Si that form the spread splat, and the alumina diffuses rapidly along the grain boundary through molten SiO 2 phase when impacting the alumina ceramic matrix 35–37 . This diffusion is beneficial to improve the bonding strength between the matrix and spray particles to a certain extent.…”

“…Combined with the oxidation phenomenon of the collected spray powder, it is the fused SiO 2 and the decomposed Si that form the spread splat, and the alumina diffuses rapidly along the grain boundary through molten SiO 2 phase when impacting the alumina ceramic matrix. [35][36][37] This diffusion is beneficial to improve the bonding strength between the matrix and spray particles to a certain extent.…”

First-principles calculation of diamond/Al interface properties and study of interface reaction

“…Monje等 [14] 通过气压浸渗和原位化学表面改性制 备了金刚石/铝复合材料, 指出清洁或重构的金刚 石表面有利于界面热传导. Li等 [15] 提出了一种在 金刚石表面低温合成SiC的新方法, SiC界面层的 引入使复合材料的导热系数提高了12.9%, 且在潮 湿环境中表现出良好的导热稳定性.…”

Simultaneously low resistance drift and ultra‐fast phase change speed based on GeSb/Sb multilayer thin films

“…16 However, F I G U R E 1 R-T graphs of GeSb/Sb multilayer films with different thickness ratios and pure Sb films. its multiple phase structures (amorphous phase: stable and substable states 17 ; crystalline phase: Face centered cubic (FCC) and Hexagonal close-packed (HCP) states 18 ) result in a large resistance drift of its two states, which reduces the accuracy of information reading. 19 Moreover, the growth-dominated crystallization mechanism of GST also leaves much room for improvement of its phase transition rate (SET time > 150 ns of GST).…”

“…As the most mature phase change material in the field of PCRAM, GeSbTe (GST) (Ge 2 Sb 2 Te 5 ) thin film has the advantages of strong fatigue performance, irradiation resistance, and large difference in optoelectronic properties between amorphous and crystalline states 16 . However, its multiple phase structures (amorphous phase: stable and substable states 17 ; crystalline phase: Face centered cubic (FCC) and Hexagonal close‐packed (HCP) states 18 ) result in a large resistance drift of its two states, which reduces the accuracy of information reading 19 . Moreover, the growth‐dominated crystallization mechanism of GST also leaves much room for improvement of its phase transition rate (SET time > 150 ns of GST) 20 .…”