Enhancement of oxidation rate of a-Si nanoparticles during dehydrogenation

Das, Debabrata; Farjas, Jordi; Roura, P.; Viera, G.; Bertrán, E.

doi:10.1063/1.1420533

Cited by 18 publications

(12 citation statements)

References 16 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…This result is independent of the initial local environment. 7 On the other hand, we have reported in a recent work 22 that oxidation occurs at low temperature in our nanoparticles (TϽ300°C). Oxygen is mainly incorporated at dangling bond sites.…”

Section: Analysis and Discussionmentioning

confidence: 95%

Calorimetry of hydrogen desorption froma-Si nanoparticles

et al. 2002

Self Cite

View full text Add to dashboard Cite

The process of hydrogen desorption from amorphous silicon (a-Si͒ nanoparticles grown by plasmaenhanced chemical vapor deposition ͑PECVD͒ has been analyzed by differential scanning calorimetry ͑DSC͒, mass spectrometry, and infrared spectroscopy, with the aim of quantifying the energy exchanged. Two exothermic peaks centered at 330 and 410°C have been detected with energies per H atom of about 50 meV. This value has been compared with the results of theoretical calculations and is found to agree with the dissociation energy of Si-H groups of about 3.25 eV per H atom, provided that the formation energy per dangling bond in a-Si is about 1.15 eV. It is shown that this result is valid for a-Si:H films, too.

show abstract

Section: Analysis and Discussionmentioning

confidence: 95%

Calorimetry of hydrogen desorption froma-Si nanoparticles

et al. 2002

Self Cite

View full text Add to dashboard Cite

show abstract

“…This second thermogram was subtracted from the first one in order to correct it for the apparatus baseline. Due to the sensitivity of nanoparticles to low-temperature oxidation, 35 the sample mass was measured before and after the experiment. If after correction by the mass loss due to dehydrogenation a significant mass gain due to oxidation was detected, the thermogram was rejected.…”

Section: Methodsmentioning

confidence: 99%

“…In the case of nanoparticles, one possible explanation could be the contribution of the low-temperature oxidation process previously reported. 35 Although special care has been taken, a minor oxidation level could affect the measured enthalpy, owing to its highly exothermic character ͓9.32 eV/͑Si atoms͒ ͑Ref. 52͔͒.…”

Section: B Enthalpy Of Dehydrogenation Of the Low-temperature Processesmentioning

confidence: 99%

Calorimetry of dehydrogenation and dangling-bond recombination in several hydrogenated amorphous silicon materials

et al. 2006

Self Cite

View full text Add to dashboard Cite

Differential scanning calorimetry ͑DSC͒ was used to study the dehydrogenation processes that take place in three hydrogenated amorphous silicon materials: nanoparticles, polymorphous silicon, and conventional device-quality amorphous silicon. Comparison of DSC thermograms with evolved gas analysis ͑EGA͒ has led to the identification of four dehydrogenation processes arising from polymeric chains ͑A͒, SiH groups at the surfaces of internal voids ͑AЈ͒, SiH groups at interfaces ͑B͒, and in the bulk ͑C͒. All of them are slightly exothermic with enthalpies below 50 meV/͑H atoms͒, indicating that, after dissociation of any SiH group, most dangling bonds recombine. The kinetics of the three low-temperature processes ͓with DSC peak temperatures at around 320 ͑A͒, 360 ͑AЈ͒, and 430°C ͑B͔͒ exhibit a kinetic-compensation effect characterized by a linear relationship between the activation entropy and enthalpy, which constitutes their signature. Their Siu H bond-dissociation energies have been determined to be E͑Siu H͒ 0 = 3.14 ͑A͒, 3.19 ͑AЈ͒, and 3.28 eV ͑B͒. In these cases it was possible to extract the formation energy E͑DB͒ of the dangling bonds that recombine after Siu H bond breaking ͓0.97 ͑A͒, 1.05 ͑AЈ͒, and 1.12 ͑B͔͒. It is concluded that E͑DB͒ increases with the degree of confinement and that E͑DB͒ Ͼ 1.10 eV for the isolated dangling bond in the bulk. After Siu H dissociation and for the low-temperature processes, hydrogen is transported in molecular form and a low relaxation of the silicon network is promoted. This is in contrast to the high-temperature process for which the diffusion of H in atomic form induces a substantial lattice relaxation that, for the conventional amorphous sample, releases energy of around 600 meV per H atom. It is argued that the density of sites in the Si network for H trapping diminishes during atomic diffusion.

show abstract

“…Great attention has been paid to remove oxygen from the DSC furnace atmosphere because oxidation is enhanced during dehydrogenation of a-Si:H. 7 For a "nominally" inert N 2 atmosphere, we always obtained a high exothermic signal extending up to the crystallization temperature ͑Ϸ700°C͒. 8,9 This signal disappeared when more inert conditions were used ͑higher N 2 flow rates͒ revealing a less intense signal containing endothermic contributions ͑Fig.…”

mentioning

confidence: 99%

Relaxation and derelaxation of pure and hydrogenated amorphous silicon during thermal annealing experiments

Kail

Farjas

Roura

et al. 2010

Applied Physics Letters

Self Cite

View full text Add to dashboard Cite

The structural relaxation of pure amorphous silicon ͑a-Si͒ and hydrogenated amorphous silicon ͑a-Si:H͒ materials, that occurs during thermal annealing experiments, has been analyzed by Raman spectroscopy and differential scanning calorimetry. Unlike a-Si, the heat evolved from a-Si:H cannot be explained by relaxation of the Si-Si network strain but it reveals a derelaxation of the bond angle strain. Since the state of relaxation after annealing is very similar for pure and hydrogenated materials, our results give strong experimental support to the predicted configurational gap between a-Si and crystalline silicon.

show abstract

Enhancement of oxidation rate of a-Si nanoparticles during dehydrogenation

Cited by 18 publications

References 16 publications

Calorimetry of hydrogen desorption froma-Si nanoparticles

Calorimetry of hydrogen desorption froma-Si nanoparticles

Calorimetry of dehydrogenation and dangling-bond recombination in several hydrogenated amorphous silicon materials

Relaxation and derelaxation of pure and hydrogenated amorphous silicon during thermal annealing experiments

Contact Info

Product

Resources

About