H.H. Lin

Evolution of structural order in germanium ion-implanted amorphous silicon layers

High-resolution transmission electron microscopy in conjunction with autocorrelation function analysis have been applied to investigate the evolution of structural order in germanium ion-implanted amorphous silicon (a-Si) layers. A high density of Si nanocrystallites as small as 1 nm in size was detected in as-implanted a-Si layers. The density of embedded nanocrystalline Si was found to diminish in a-Si layers with annealing temperature first then increase. The results are discussed in the context of free energy change with annealing temperature.

Ultrafast directional nickel-silicide-induced crystallization of amorphous silicon under high-density current stressing

Ultrafast directional crystallization that combined the electric current stressing with metal-induced crystallization has been achieved for BF2+-implanted amorphous Si (a-Si) at room temperature. Polycrystalline Si was observed to grow from anode towards cathode and the channels of a-Si strips with a length of 140 μm and a width of 10 μm can be fully crystallized with a stressing time less than 0.2 s. The directional growth of crystalline Si nanowires, 50 nm in width and as long as 3 μm in length, with an extraordinarily high aspect ratio of 60, indicates a strong electric-field-induced effect on the growth. The growth method provides a promising scheme to solve the problems caused by high-temperature and long-term annealing treatment for the applications of optoelectronic devices.

Effects of titanium and tantalum adhesion layers on the properties of sol-gel derived SrBi2Ta2O9 thin films

The effects of titanium (Ti) and tantalum (Ta) adhesion layers on the ferroelectric and microstructural properties of sol-gel-derived SrBi2Ta2O9 (SBT) films are investigated. It is found that the atoms from the adhesion layer play a significant role in the resultant microstructures and physical properties of SBT films. The electron spectroscopy for chemical analysis clearly indicates that both the Ti and Ta atoms of adhesion layers have out-diffused behavior onto the surface of bottom-electrode Pt films after a thermal treatment of 750 °C, 1 min. Various out-diffused species do cause the distinct properties of SBT films, which are confirmed by the results of surface analysis and polarization-electric field (P-E) measurements. The formation of undesirable second phase compounds near the SBT/PT interface has been observed in specimens with Ti layer, and it is speculated to be the significant degradation of spontaneous polarization. On the contrary, Ta species are found to exhibit the pure bismuth-layered st...

Structural evolution in amorphous silicon and germanium thin films.

The structural evolution in amorphous silicon and germanium thin films has been investigated by high-resolution transmission electron microscopy (HRTEM) in conjunction with autocorrelation function (ACF) analysis. The results established that the structure of as-deposited semiconductor films is of a high density of nanocrystallites embedded in the amorphous matrix. In addition, from ACF analysis, the structure of a-Ge is more ordered than that of a-Si. The density of embedded nanocrystallites in amorphous films was found to diminish with annealing temperature first, then to increase. The conclusions also corroborate well with the results of diminished medium-range order in annealed amorphous films determined previously by a variable coherence microscopy method.

Enhanced dopant activation and elimination of end-of-range defects in BF2+-implanted silicon-on-insulator by high-density current

Enhanced dopant activation and elimination of end-of-range (EOR) defects in BF2+-implanted silicon-on-insulator (SOI) have been achieved by high-density current stressing. With the high-density current stressing, the implantation amorphous silicon underwent recrystallization, enhanced dopant activation and elimination of the (EOR) defects. The current stressing method allows the complete removal of EOR defects that has not been possible with conventional thermal annealing in the processing of high-performance SOI devices.

Influence of Ultrathin Tantalum Buffer Layers on Microstructure and Ferroelectric Properties of SrBi2Ta2 O 9 Thin Films

The effects of buffer layers on the crystallization process of strontium bismuth tantalite (SBT) thin films, using a metallorganic decomposition technique, are investigated in this study. Ultrathin tantalum (Ta) buffer layers of various thicknesses were deposited onto Pt/TiO 2 /SiO 2 /Si substrates using magnetron sputtering. The crystallinity, microstructure, and electrical properties of the resulting SBT films on top of the Ta layer were found to be strongly dependent on the thickness of the buffer layer. By optimizing this buffer layer thickness, a homogeneous bismuth-layered structure with uniformly distributed fine grains, it was clearly evident that the SBT film, annealed at 750°C for 1 min, and the corresponding remanent polarization (2P r ), can be as large as 18.8 μC/cm 2 at an applied voltage of 5 V. It is suggested that these buffer layers cause the SBT composition to depart from stoichiometry to an enriched Ta condition. During the crystallization procedure in oxygen ambient, the excess Ta atoms in local regions easily reacted with O atoms to form TaO x centers. They are believed to serve as the nucleation sites that cause the reduction of the activation energy of SBT crystallization.

Effects of ultrathin tantalum seeding layers on sol-gel-derived SrBi2Ta2O9 thin films

The effects of Ta seeding layer on the crystalline microstructure and ferroelectric properties of sol-gel-derived strontium–bismuth–tantalate (SBT) thin films were investigated. Ultrathin (<1 nm) Ta seeding layers were deposited onto Pt/TiO2/SiO2/Si substrates by magnetron sputtering at room temperature before spin coating of SBT thin films. Our results show that the presence of Ta seed layer induces significant changes in the crystallinity and microstructure of the resultant SBT thin films, resulting in improved ferroelectric properties in terms of spontaneous polarization. Interestingly, the remanent polarization (2Pr) of SBT films is also found to initially increase and then decrease with increasing Ta thickness, showing a peak value of 18.8 μC/cm2 (@5 V) at Ta thickness of around 0.23 nm. Since a stoichiometric SBT solution was employed in our experiments, the additional Ta on the Pt surface is thought to provide a Ta-rich environment for SBT films, which, in turn, results in lower nucleation activati...

The failure mechanisms and phase formation for Ni, Co and Cu contacts on ion implanted (001)Si under high current stress

Abstract Ultrafast diffusion of Ni and Cu atoms in p+-Si channel was observed. Contact failed at negative contact first, possibly by electron–hole recombination at the negative electrode. Ti diffusion assisted by Cu under high current density was observed in the Cu and Ti multilayered samples. Ti atoms at Ti contact cannot migrate into the diffusion channel but can be carried by Cu atoms. In addition, Cu and Ti easily interdiffused under high current density.

Electromigration of Cu and Ti atoms and dopant junction profiles in the p+-Si implanted channel under high-density current

Abstract Ultrafast diffusion of Cu and Ti atoms in p + -Si channel was achieved in samples stressed with high current density. The junction was changed under high current stress and copper silicide was formed in the junction. The current effects of high current on the silicide line formation and symmetrical end-of-range defects elimination near the center of p + -Si channel are discussed.