DC-electric-field-modified second-harmonic generation at the Si(100) surface

1 resonances for clean and H covered surfaces shift as a function of the dc field in agreement with experiment. This suggests the presence of built-in electric fields whose strength depends on the H coverage, and which are strongly localized in the subsurface region. Received: 20 September 1998     

Local atomic environment of Si suboxides at the SiO2/Si(111) interface determined by angle-scanned photoelectron diffraction

Local environments of Si suboxides at the interface between a thermally grown SiO2 film and Si(111) were studied by angle-scanned photoelectron diffraction. Si 2p core-level spectra containing chemically shifted components were recorded. The components were deconvoluted by least squares fitting and assigned to different Si oxidation states. The obtained diffraction patterns of the various suboxides exhibit different features. Comparison of these patterns with multiple scattering calculations including a multipole R-factor analysis shows that a simple chemical abrupt interface model describes well the environment of the suboxides and indicates ordered SiO2 close to the interface.     

ESR observation of phosphorus pile-up at the Si/SiO2 interface in boron-doped Si

It is shown that dry thermal oxidation of B-doped (p-type) CZ-grown Si wafers may create P-rich near-interfacial Si layers. Thermal treatments were mostly carried out at T_ox=950±20°C for times 3 ≲ t_ox ≲ 7 h in either a 0.11 MPa high-purity O₂ ambient or strongly-reduced O₂ pressure (p_o2 ≲ 13 mPa). The existence of such layers was discovered by sensitive low T ESR observations, revealing the typical P³¹-in-(n-type) Si spectrum. These measurements in combination with selective etching experiments and number-of-spins determinations showed these surface layers to be actually semiconductor-type reversed. It is argued that the P atoms collected at the Si/SiO₂ interface during thermal treatments are inherently present as bulk impurities in the as-received Si.     

Optical second-harmonic investigations of the isothermal desorption of SiO from the Si(100) and Si(111) surfaces

The isothermal desorption of SiO from the Si(100) and Si(111) surfaces was investigated by means of optical second-harmonic generation (SHG). Due to the high adsorbate sensitivity of this method, desorption rates could be measured over a wide range from 10⁻¹ to 10⁻⁶ ML s⁻¹. From their temperature dependence between 780 and 1000 K, activation energies of E_A=3.4±0.2 eV and E_A=4.0±0.3 eV and pre-exponential factors of ν₀=10^16±1 s⁻¹ and ν₀=10^20±1 s⁻¹ for SiO desorption were obtained for Si(100) and Si(111), respectively. In the case of the Si(100) surface, a pronounced decrease of the first-order rate constants was observed upon increasing the initial coverage from 0.02 to 0.6 ML. The results are interpreted in terms of coverage-dependent oxygen-binding configurations, which influence the stability of the oxide layer.