Hydrogen passivation of interfacial gap state defects at UHV-prepared ultrathin SiO2 layers on Si(111), Si(110), and Si(100)

Ultra-thin silicon oxide layers on crystalline silicon wafers: Comparison of advanced oxidation techniques with respect to chemically abrupt SiO 2 /Si interfaces with low defect densities

“…WCO-NAOS is known to increase the micro-roughness of the Si surface leading to defects during SiO 2 /Si interface formation, that facilitate recombination [54]. PO is assumed to induce damages on the Si surface caused by energetic ion bombardment during oxidation and, thereby, increasing the density of interface states [37,41]. TPO has the advantage of using neutral oxygen atoms leading to a reduction of dangling bonds and fixed charges in the oxide layer and a homogeneous oxide microstructure [22].…”

“…Plasma oxidation with thermalized neutral oxygen atoms (TPO) will be included in the techniques to be considered, since it has been demonstrated to produce abrupt interfaces with low densities of interface states, even at low substrate temperatures of <600 °C [37][38][39]. By means of remote plasma, atomically flat silicon oxide monolayers can be also produced [40].…”

Effect of wet-chemical substrate smoothing on passivation of ultrathin-SiO2/n-Si(111) interfaces prepared with atomic oxygen at thermal impact energies

“…Further interface optimisation was achieved by successive hydrogenation using the same plasma cracker source to produce atomic hydrogen with thermal energies (E kin <1 eV). The low-energy impact of the impinging H atoms results in an effective passivation of dangling bonds at the interface without further defect generation [1,26]. …”

“…In photovoltaics, ultrathin SiO 2 layers have been successfully demonstrated to act as functional elements in various innovative solar cell concepts: e.g., as passivation layers [1,2], as substrates for the deposition of organic molecules [3], and (iii) as barrier in Si/SiO 2 quantum well structures [4]. Main challenge for those applications is the question of whether stable, homogeneous, ultrathin SiO 2 layers produced on silicon with both structurally abrupt interfaces and low density of defect states.…”

“…It was shown, that the substrate surface conditioning has to be carefully optimized with respect to the substrate morphology and the subsequent layer preparation [13]. In this contribution we report on the preparation of ultrathin SiO 2 layers in the range of 9 -15 Å on c-Si substrates by wet-chemical treatment with various specific oxidizing solutions and successive novel oxidation with neutral atomic oxygen from a remote plasma cracker source under ultrahigh vacuum conditions, which has proven to produce high-quality Si/SiO 2 interfaces [1,2]. The effects of wet-chemical substrate pre-treatment, oxidation and annealing processes on the electronic properties of the Si/SiO 2 interface were investigated.…”