ESR of residual defects in silicon from recoil implantation of oxygen in Si/SiO2 systems

In ionic crystals or other insulators with partial ionic binding, the ion-target interaction differs from that of neutral atoms due to different electronic distributions and overall electrical charges Consequently, the nuclear stopping power and defect production by recoiling atoms will deviate from standard values, obtained from e g Moliere-potentials In the present paper, realistic potentials between projectile ion and target ion are determined by the free electron gas model of overlapping Hartree-Fock-Slater or Lenz-Jensen ions (and neutral atoms for comparison) With the new potentials, the transferred energies T and the range of interaction is determined for either damage production (T>E_d) and for nuclear stopping (T>hω> for bound ions) In addition the excitation of optical phonons is taken into account which are excited by the transient electrical field of the charged projectile     

Diffusion measurement of implanted Sb into Si,using SiO2 encapsulation

Large, asymmetric atomic relaxations have been shown to play a crucial role in the structure and properties of several point defects in oxide materials. Examples include trapped hole centers in alkaline-earth oxides and E1′ and E4′ oxygen-vacancy centers and peroxy-radical defects in silicon dioxide. Schirmer's “bound small polaron” model, applied in particular to the alkaline-earth oxide defects, and model treatments of the E1′ center in SiO2 by Yip, Griscom and Fowler clearly illustrate the important spectroscopic consequences of such atomic relaxations. In fact, such effects had been incorporated in Lüty's classic model of the Type II FA center in alkali halides. Edwards and Fowler have recently applied MNDO and MINDO/3 quantum-chemistry approaches to the E1′, E4′, and peroxy radical defects in SiO2. These calculations generally corroborate suggested models and bear as well on possible creation mechanisms. Large relaxation effects are likely to be important in many other defects in oxide materials.     

Excess Si concentration dependence of the photoluminescence of Si nanoclusters in SiO2 fabricated by ion implantation

A method for the fabrication of luminescent Si nanoclusters in an amorphous SiO₂ matrix by ion implantation and annealing, and the detailed mechanisms for the photoluminescence are reported. We have measured the implanted ion dose, annealing time and excitation energy dependence of the photoluminescence from implanted layers. The samples were fabricated by Si ion implantation into SiO₂ and subsequent high-temperature annealing. After annealing, a photoluminescence band below 1.7 eV has been observed. The peak energy of the photoluminescence is found to be independent of annealing time and excitation energy, while the intensity of the luminescence increases as the annealing time and excitation energy increase. Moreover, we found that the peak energy of the luminescence is strongly affected by the dose of implanted Si ions especially in the high dose range. These results indicate that the photons are absorbed by Si nanoclusters, for which the band-gap energy is modified by the quantum confinement effects, and the emission is not simply due to direct electron–hole recombination inside Si nanoclusters, but is related to defects probably at the interface between Si nanoclusters and SiO₂, for which the energy state is affected by Si cluster–cluster interactions. It seems that Si nanoclusters react via a thin oxide interface and the local concentrations of Si nanoclusters play an important role in the peak energy of the photoluminescence.     

重离子辐照SiO_2/Si结构变温光致发光谱研究

本文研究了重离子辐照前后SiO_2/Si结构光学性质的变化。实验选择初始能量为414 MeV,不同辐照总剂量的Sn离子,在室温下辐照氧化层厚度为36nm和90nm的SiO_2/Si结构。并在不同测试温度下获得了辐照前后SiO_2/Si结构的光致发光谱(PL)谱。在相同的测试温度下,随着辐照总剂量的改变,峰位发生了移动,峰的强度也发生了改变;在相同的辐照总剂量下,随着测试温度的改变,峰位发生移动。由于受束缚激子发光的影响,在测试温度为80K时出现了一个新的光致发光峰。     

Correlation of size and oxygen bonding at the interface of Si nanocrystal in Si–SiO2 nanocomposite: A Raman mapping study

Raman spectroscopy/mapping is used to investigate the variation of Si phonon wavenumbers, i.e., lower wavenumber (LW ~ 495–510 cm⁻¹) and higher wavenumber (HW ~ 515–519 cm⁻¹) phonons, observed in Si–SiO₂ multilayer nanocomposite (NCp) grown using pulsed laser deposition. Sensitivity of Raman spectroscopy as a local probe to surface/interface is effectively used to show that LW and HW phonons originate at surface (Si–SiO₂ interface) and core of Si nanocrystals, respectively. The consistent picture of this understanding is developed using Raman spectroscopy monitored laser heating/annealing and cooling experiment at the site of the desired wavenumber, chosen with the help of Raman mapping. Raman spectra calculations for Si₄₁ cluster with oxygen and hydrogen termination show strong mode at 512 cm⁻¹ for oxygen terminated cluster corresponding to the vibration of surface Si atoms. This supports our attribution of LW phonons to be originating at the Si–SiO₂ surface/interface. These results along with XPS show that nature of interface (oxygen bonding) in turn depends on the size of nanocrystals and LW phonons originate at the surface of smaller Si nanocrystals. The understanding developed can conclude the ongoing debate on large variation in Si phonon wavenumbers of Si–SiO₂ NCps in the literature. Copyright © 2015 John Wiley & Sons, Ltd.