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Solid state reaction of Co/a-Si/Ti/Si(100) was used to investigated epitaxial growth of CoSi2.

We report a simulation of quantum cascade lasers based on the integration of a number of optoelectronic models on both microscopic and macroscopic scales. On the microscopic scale, quantum mechanical computation was performed to find the quantization states and a rate equation approach was used to compute the optical gain. On the macroscopic scale, we solved the drift-diffusion equations with modification of current density to account for long-range carrier transport, including quantum tunneling, mini-band tunneling, and hot carrier transport. Multiple lateral optical modes were computed by solving a scalar wave equation as an eigenvalue problem. Finally, multiple lateral mode laser cavity photon rate equations were solved with the drift-diffusion equations in a self-consistent manner to predict the lasing characteristics of a quantum cascade laser. The simulation compared the integrated models with experimental data from a number of AlInGaAs/InP systems with variable quantum wells and at different temperatures. Reasonable agreements with experiments have been obtained for both electrical and lasing characteristics. [ABSTRACT FROM AUTHOR]

This work reports a first-principles study of copper adhesion on Ta(110) and Ru(0001) surface with the density functional theory. Adsorption energy, electron density difference, and geometrical structures of Cu on pure, oxygen, and nitrogen doped Ta(110), Ru(0001) surfaces, and Ru doped Ta(110) surface were investigated. By analyzing the calculated results and the existing experimental results, it is found that although Ta has stronger chemical interaction with Cu, its larger lattice mismatch with Cu, and easy oxidation and nitridation make Ta a poorer Cu adhesion layer in comparison with Ru. The adhesion ability of Cu on Ta can be improved by doping Ru in Ta. The agglomeration of Cu on Ta or Ru is also studied. The calculation results show that Cu adsorbed on Ta(110) surface is more likely to be desorbed and agglomerated on the top of the second Cu atom layer. The substitutional oxygen OTa in Ta will stimulate the agglomeration of Cu on the Ta surface. [ABSTRACT FROM AUTHOR]

This work investigates the effects of postannealing on the electrical properties of the n-ZnO nanorods/p-Si heterojunction. Well-aligned ZnO nanorods are grown on the p-Si substrate with a ZnO seed layer through a hydrothermal method. The as-grown ZnO nanorods are grown along the preferential [0001] direction with high single crystalline quality. The rectifying characteristics of the heterojunction are effectively improved and the rectification ratio is increased tens of times after annealing in air. The leakage current is decreased by two orders of magnitude and the forward-bias injection efficiency is largely enhanced after annealing. The photoluminescence and x-ray photoelectron spectroscopy results show that annealing in the air ambient can effectively reduce the loosely adsorbed oxygen on the surface of the ZnO nanorods so that the bound free electrons can be released, which can result in larger carrier concentration and improve the injection efficiency of the n-ZnO nanorods/p-Si structure in the forward voltage. [ABSTRACT FROM AUTHOR]

Atomic layer deposition (ALD) of TiO2 thin films using Ti isopropoxide and tetrakis-dimethyl-amido titanium (TDMAT) as two kinds of Ti precursors and water as another reactant was investigated. TiO2 films with high purity can be grown in a self-limited ALD growth mode by using either Ti isopropoxide or TDMAT as Ti precursors. Different growth behaviors as a function of deposition temperature were observed. A typical growth rate curve-increased growth rate per cycle (GPC) with increasing temperatures was observed for the TiO2 film deposited by Ti isopropoxide and H2O, while surprisingly high GPC was observed at low temperatures for the TiO2 film deposited by TDMAT and H2O. An energetic model was proposed to explain the different growth behaviors with different precursors. Density functional theory (DFT) calculation was made. The GPC in the low temperature region is determined by the reaction energy barrier. From the experimental results and DFT calculation, we found that the intermediate product stability after the ligand exchange is determined by the desorption behavior, which has a huge effect on the width of the ALD process window. [ABSTRACT FROM AUTHOR]

A thin amorphous Si (α-Si) interlayer is produced between the sputtering deposited ytterbium layer and Si(001) substrate, and the growth of the ytterbium silicide (YbSi2-x) film is investigated in this paper. Formation of YbSi2-x was verified by x-ray diffraction (XRD). The silicide film morphology was examined by scanning electron microscopy (SEM) and atomic force microscopy (AFM). SEM results reveal that without the α-Si interlayer, pinholes form during YbSi2-x formation on Si(001). Furthermore, the XRD results demonstrate that there is a strong epitaxial relationship between the formed YbSi2-x and Si(001) substrate, and it is believed to be the reason for the formation of pinholes. To suppress the formation of pinholes, a thin α-Si interlayer with different thicknesses is introduced on the Si(001) substrate prior to Yb film deposition. The α-Si interlayer is produced by either sputter deposition employing a Si target or by Si ion implantation induced amorphization. In the presence of this thin α-Si interlayer, epitaxial growth of YbSi2-x is greatly suppressed even when the α-Si interlayer is so thin that full silicidation of the deposited Yb film still requires consumption of Si atoms from the Si(001) substrate. Fabrication of a pinhole-free YbSi2-x film is also demonstrated by SEM and AFM. The growth mechanism of the pinhole-free YbSi2-x film in the presence of a thin α-Si interlayer is discussed. [ABSTRACT FROM AUTHOR]

Different from the conventional current-voltage and capacitance-voltage methods, Schottky contact barrier height extraction by admittance measurement is proposed and discussed in this paper. In this method, the barrier height can be simply extracted from the difference between the measured admittance at zero bias and a reasonably high forward bias. Both simulation results and experimental data demonstrate that the proposed method is effective not only for extraction of Schottky contacts with higher barrier heights (>0.4 eV) but also for extraction of those with moderately lower barrier heights (0.2–0.4 eV). [ABSTRACT FROM AUTHOR]

The temperature-dependent current-voltage (I-V-T) technique has been used to study the Ni/Si solid phase reaction by measuring the Schottky barrier height (SBH) inhomogeneity of Ni-silicide/ Si Schottky diodes. The experimental results show the strong dependence of SBH inhomogeneity on the Ni/Si solid phase reaction. The SBH distribution of the diodes annealed at 500 and 600 °C can be described by a single-Gaussian function and the diode annealed at 500 °C is found to have the best homogeneity and the smallest leakage current. The SBH distribution of the diodes annealed at 400, 700, and 800 °C can be described by a double-Gaussian function in which the mean value of the second Gaussian function is substantially smaller than that of the dominant Gaussian function. The variation of SBH inhomogeneity, an interface property, is related to the phase evolution process in the Ni/Si solid phase reaction, and verified by reverse I-V measurements. Our results indicate that the I-V-T technique may be developed as a wafer-level testing tool to monitor the silicidation process in the complementary metal-oxide-semiconductor device fabrication. [ABSTRACT FROM AUTHOR]

Epitaxial growth of CoSi[sub 2] by solid state reaction of Co/a-Si/Ti/Si(100) is investigated. A Ti/a-Si composite interlayer is used to modify the diffusion barrier and influence the epitaxial growth process. The epitaxial quality of the CoSi[sub 2] is improved compared to the film grown by Co/Ti/Si reaction. A multielement amorphous layer is formed by a solid-state amorphization reaction at the initial stage of the multilayer reaction. This layer acts as a diffusion barrier, which controls the atomic interdiffusion of Co and Si while limiting the supply of Co atoms. CoSi[sub 2] grows as the first phase and the growth interface of the epitaxial CoSi[sub 2] is at both the CoSi[sub 2]/Si and CoSi[sub 2]/CoSi interfaces. Investigation of the growth kinetics shows that the activation energy of CoSi[sub 2] formation is larger than that without an amorphous Si layer. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]