A structural interpretation of SiOSi vibrational absorption of high-photoconductive amorphous a-SiOx:H films

Haga, Koichi; Watanabe, Hideo

doi:10.1016/0022-3093(95)00544-7

Cited by 43 publications

(34 citation statements)

References 14 publications

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“…This controversy stems from experimental evidences showing that in SiO x thin films with a given O / Si ratio, different distributions of oxidation states can be found according to the method of preparation. 12,16,17 Thus, in previous works, we have found that SiO x thin films deposited at room temperature by evaporation of silicon monoxide do not follow the distribution of Si n+ states predicted by the RBM. 10,12,18 We also showed that these SiO x films were in a metastable state and that either by light excitation 12 or ion-beam irradiation 19 the distribution of Si n+ species may change while keeping constant the overall O / Si ratio.…”

Section: Introductionmentioning

confidence: 99%

“…Most experimental procedures employed for the preparation of SiO x thin films are based on chemical or physical phenomena that, directly or indirectly, may induce some kind of excitation of the growing layers. This is the case of sputtering 13 or plasma processes 16,20,21 where ion bombardment, UV-light irradiation, or the supply of thermal energy might lead to a redistribution of oxidation states in the SiO x thin films and, therefore, to changes in their properties. Since the influence of these processes is not well controlled or even recognized, a comparison of the published results on SiO x prepared by different procedures is not always straightforward.…”

Section: Introductionmentioning

confidence: 99%

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Electronic state characterization of SiOx thin films prepared by evaporation

Barranco

Yubero

Espinós

et al. 2005

Journal of Applied Physics

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SiO x thin films with different stoichiometries from SiO 1.3 to SiO 1.8 have been prepared by evaporation of silicon monoxide in vacuum or under well-controlled partial pressures of oxygen ͑P Ͻ 10 −6 Torr͒. These thin films have been characterized by x-ray photoemission and x-ray-absorption spectroscopies, this latter at the Si K and L 2,3 absorption edges. It has been found that the films prepared in vacuum consists of a mixture of Si 3+ and Si + species that progressively convert into Si 4+ as the partial pressure of oxygen during preparation increases. From this spectroscopic analysis, information has been gained about the energy distribution of both the full and empty states of, respectively, the valence and conduction bands of SiO x as a function of the O / Si ratio. The characterization of these films by reflection electron energy-loss spectroscopy ͑REELS͒ has provided further evidences about their electronic structure ͑band gap and electronic states͒ as a function of the oxygen content. The determination of the plasmon energies by REELS has also shown that the films prepared by evaporation in vacuum consist of a single phase which is characterized by a density ͑1.7 g cm −3 ͒ lower than that of SiO 2 ͑i.e., 2.2 g cm −3 ͒ or Si ͑i.e., 2.4 g cm −3 ͒. The optical properties ͑n and k͒ of the films as a function of the O / Si content have been deduced from the analysis of REELS spectra in the energy range from 4 to 20 eV. It has been also shown that the O / Si ratio in the films and several spectroscopic parameters such as the Auger parameter or the energy of bulk plasmons present a linear relationship and that this linear dependence can be used for a rapid characterization of SiO x materials. By contrast, the band-gap energy changes differently with the O / Si ratio, following a smooth linear increase from about 3.8 eV for SiO 1.3 to ca. 5.0 eV for SiO 1.7 and a jump up to 8.7 eV for SiO 2 . These results indicate that the random-bonding model does not apply to thin films prepared by evaporation under our experimental conditions. Other distributions of Si n+ states can be induced if the films are excited with an external source such as heat or photon irradiation. In this case the electronic properties vary and the previous linear correlations as a function of the oxygen content do not hold any longer.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Electronic state characterization of SiOx thin films prepared by evaporation

Barranco

Yubero

Espinós

et al. 2005

Journal of Applied Physics

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“…We also propose an influence of the material dielectric constant due to increased O concentrations as an explanation of the increase of the Si-O-Si vibrational frequencies with increasing oxygen concentration c O [15]. We also note the possibility of inhomogeneous distributions of Si and O in the a-SiO x :H films, which may consist of a two-phase structure [16]. Upon annealing, the Si and O rich phases of such films can further segregate and form SiO 2 -rich clusters [17,18].…”

Section: Infrared Absorptionmentioning

confidence: 95%

Annealing studies of substoichiometric amorphous SiO_x layers for c‐Si surface passivation

Einsele

Beyer

Rau

2010

Phys. Status Solidi (c)

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We investigate thermal stability of amorphous substoichiometric silicon‐oxide alloys with oxygen concentrations from 0 to 10 at‐%. Annealing experiments, including effective lifetime measurements, hydrogen effusion, and infrared absorption spectroscopy, yield a surface passivation on p‐type float‐zone crystalline silicon wafers with maximum effective lifetimes up to 1.5 ms. The thermal stability of the passivation increases with increasing oxygen concentration of the films. For oxygen concentrations above 5%, we observe a decrease of passivation due to the formation of voids in the material, which shows in a low temperature peak of the H effusion spectra. Annealing leads to a structural transition of the material which is accompanied by an increase in effective lifetime. The stretching mode absorptions of Si– O–Si molecular vibrations near 1000 cm–1 shift towards higher wavenumbers, both with increased oxygen concentration and upon annealing of the films. For increased oxygen concentrations, the Si–H stretching modes shift from predominantly 2000 cm–1 to 2090 cm–1(© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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“…Thus, any oligomerization of large radicals that could occur under S conditions has not been detected. The mass spectra indicated that the products created during the fragmentation of D4 were similar to those from M2, 15 and a molecule of ethylene. This reaction could also be possible as the mass histogram (Fig.…”

Section: Hmdso Plasmasmentioning

confidence: 97%

“…The frequency of its maximal intensity is~1015 cm ±1 for M2H, and~1030 cm ±1 for D4H. That these frequencies are lower than that of fused silica (~1075 cm ±1 ) is due to a lower oxygen concentration, x, in a-SiO x :H. [15] The Si/O atomic ratio is 2 in M2 and 1 in the D4 monomer, whereas an excess of O 2 is known to be necessary to reach stoichiometric silica SiO 2 . Refractive indices, measured by ellipsometry on M2H and D4H films deposited on silicon wafers, are 1.47 and 1.52, respectively.…”

Section: Hmdso Plasmasmentioning

confidence: 99%

In-Situ Mass Spectrometry Analyses of the Fragmentation of Linear and Cyclic Siloxanes in a Glow Discharge Compared with Ex-Situ FTIR Analyses of the Deposits

Rouessac¹,

Roualdès²,

Durand³

2002

Chem. Vap. Deposition

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Mass Spectrometry (MS) analyses, up to 300 amu, were performed on linear hexamethyldisiloxane (HMDSO) and cyclic octamethylcyclotetrasiloxane (OMCTSO) vapors in low frequency plasmas (40 kHz). The fragmentation rates of the precursors, and possible oligomerization in the gas phase, depend on the plasma power. Two extreme plasma power conditions were compared: a high plasma power density and a low plasma power density, corresponding to silica-like and polymer-like film deposition conditions, respectively. The results of ex-situ Fourier transform infrared spectroscopy (FTIR) analyses can be explained by the plasma composition analyzed by MS.

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A structural interpretation of SiOSi vibrational absorption of high-photoconductive amorphous a-SiOx:H films

Cited by 43 publications

References 14 publications

Electronic state characterization of SiOx thin films prepared by evaporation

Electronic state characterization of SiOx thin films prepared by evaporation

Annealing studies of substoichiometric amorphous SiO_x layers for c‐Si surface passivation

In-Situ Mass Spectrometry Analyses of the Fragmentation of Linear and Cyclic Siloxanes in a Glow Discharge Compared with Ex-Situ FTIR Analyses of the Deposits

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A structural interpretation of SiOSi vibrational absorption of high-photoconductive amorphous a-SiOx:H films

Cited by 43 publications

References 14 publications

Electronic state characterization of SiOx thin films prepared by evaporation

Electronic state characterization of SiOx thin films prepared by evaporation

Annealing studies of substoichiometric amorphous SiOx layers for c‐Si surface passivation

In-Situ Mass Spectrometry Analyses of the Fragmentation of Linear and Cyclic Siloxanes in a Glow Discharge Compared with Ex-Situ FTIR Analyses of the Deposits

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Annealing studies of substoichiometric amorphous SiO_x layers for c‐Si surface passivation