Papers by Author: Gong Ping Li

Abstract: The deposition of a single Cu cluster on the Si (001) and Si (111) surfaces was studied by molecular dynamics simulations. EAM, SW and Morse potentials were used to describe the interaction of Cu-Cu, Si-Si, and the Cu-Si atoms, respectively. The results show that the crystallographic surface of the substrate had a large effect on film growth. On the Si (111) surface, the cluster structure demonstrate good uniformity and epitaxial relation to the substrate. There is no appreciable intermixing or silicide formation at the film-substrate interface, nor silicon segregation on the surface with incident energy between 0.1 and 1.0eV/atom. However, as the incident energy increases to 3.0eV/atom, intermixing began to appear for Cu₁₃ and Cu₁₉ clusters. For the Cu₁₄₇ cluster intermixing starts to appear at a lower energy of 1.6eV/atom. In contrast, intermixing appears on the Si (001) surface for a range of incident energy from 0.1 to 3.0eV/atom for all the three clusters studied. Furthermore, the epitaxial relation with the Si substrate result in (001)- or (111)-oriented Cu clusters on Si (001) or Si (111), respectively. This behavior is consistent with experimental observations. We found that the effect of cluster deposition on film property depends not only on the substrate-film material combination and cluster size but also on the substrate crystallographic orientation and incident energy.

Abstract: The Cu thin films were deposited on P type Si (111) substrates by ionized cluster beam (ICB) technique. The surface properties and atomic binding energy of Cu thin films were studied by X-ray Photoelectron Spectroscopy (XPS). The results show that for all XPS spectra of Cu/SiO₂/Si (111) samples deposited by neutral cluster and ionized cluster beam (V_a=5 kV), the atomic binding energy of the films was no differences with bulk materials. The reason may be that the local energy deposition and atomic restructuring caused by surface treatment process resulting in the XPS spectra of the copper films was similar with bulk standard copper.

Abstract: The Cu thin films were prepared at room temperature by radio frequency magnetron sputtering on p-type Si (111) substrates. The surface morphology and interface reaction of Cu thin films were studied at different deposition condition by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results show that the existence of the native silicon oxide layer suppresses the interdiffusion and interface reaction of Cu and Si. The formation of the copper-silicide phase is observed by XRD when the annealing temperature arrives at 450 °C.

Abstract: The Cu thin films were deposited on P type Si (111) substrates by ionized cluster beam (ICB) technique. The surface morphology and roughness of Cu thin films were studied at different deposition condition by atomic force microscopy (AFM). The results show that the average grain size and surface roughness of the Cu thin films deposited at an acceleration voltage of 3 kV is smaller than other conditions.

Abstract: The Cu films were deposited on P type Si (111) substrates by ionized cluster beam (ICB) technique. The interface reaction and atomic diffusion of Cu/Si (111) system were studied at different annealing temperatures by X-ray diffraction (XRD) and Rutherford backscattering spectrometry (RBS). Some significant results were obtained: For the Cu/Si (111) samples prepared by ionized cluster beams at V_a=3 kV, the interdiffusion of Cu and Si atoms occurred in the as deposited samples. The RBS spectra features were changed with a very small extent with increasing the annealing temperature. There are no copper-silicide phases observed by XRD before and after being annealed at different temperatures. The reason may be that there is a thermally stable interface between Cu films and Si substrates formed.

Abstract: The Cu thin films have been deposited on Si(100) substrates by magnetron sputtering at room temperature. The samples were heat treated by conventional thermal annealing in different temperatures: 230°C, 350°C, 450°C and 500°C. The interface reaction and atomic diffusion of the Cu films and Si substrates between as-deposited and as-annealed at different temperatures are investigated by means of Rutherford backscattering spectrometry(RBS) and X-ray diffraction(XRD). Some significant results are obtained on the following aspects: (1) According to RBS, as-deposited Cu/Si(100) samples are not found interdiffusion, and the onset temperature of interdiffusion is 230°C. With the increase of temperature, the interdiffusion becomes more apparent. (2) After annealing at 230°C, the XRD results of the samples showed formation of Cu₃Si(300). As the annealing temperature increases, the other copper-silicide phases are formed. The main copper-silicide phase is Cu₃Si(300) after annealing at 500°C. It means that Cu₃Si is a reliable copper-silicide in a wide range for the Cu/Si(100) interface.

Abstract: The Monte Carlo(MC) and Embedded-Atoms Method(EAM) potential are employed to investigate the structures and binding energies of copper clusters. Three results are obtained: first, the copper clusters are formed by gradually increasing atoms to icosahedral surface when the temperature is 300K and the number of atoms is from 2 to 70; second, the higher the symmetries are, the more stable the structures of copper clusters are; third, copper clusters tend to be stereo construction but not planer construction when the number of atoms is less. The structure of Cu147 is three-fly-icosahedron when the system of 147 atoms reached equilibrium at 300K. And at 700K, all 500 atoms form clusters in gas phase.