Hydrogen-effusion-induced structural changes and defects in<i>a</i>-Si:H films: Dependence upon the film microstructure

Zellama, K.; Chahed, L.; Sládek, Petr; Thèye, M. L.; Bardeleben, J. H. Von; Cabarrocas, P. Roca i

doi:10.1103/physrevb.53.3804

Cited by 50 publications

(25 citation statements)

References 22 publications

(20 reference statements)

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“…The most useful technique for the identification of the particular hydrogen states is infrared ͑IR͒ absorption spectroscopy. 2 From their characteristic stretching and bending modes, the isolated monohydride ͑wSiH͒, the clustered monohydride ͓͑wSiH͒ n ͔, and the dihydride ͑vSiH 2 ͒ can be distinguished. 3,4 Recently, a new vibrational mode has been identified and associated with H atoms located at the interfaces between silicon clusters or nanocrystals and the surrounding amorphous matrix.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2006

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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.

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Section: Introductionmentioning

confidence: 99%

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

et al. 2006

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“…When films are annealed in vacuum ͑or in inert atmosphere͒, most hydrogen is lost and the density of WBs ͑measured through the Urbach tail slope͒ increases. 12 However, when the experiment is done in hydrogen plasma, which prevents intense dehydrogenation, the WB density remains unchanged. 14 So, restructuring of the Si-Si network in a-Si:H is not directly related to the network temperature but to dehydrogenation.…”

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“…͑2͒, the contribution of ⌬ would be lower than 30 J/g for all the samples. On the other hand, we know that the DB density increases up to 5 ϫ 10 19 cm −3 upon annealing at high temperature, 12 and this results in a small contribution of 4 J/g to the relaxation heat ͓formation energy of one DBϷ 1 eV ͑Ref. 8͔͒.…”

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

Kail

Farjas

Roura

et al. 2010

Applied Physics Letters

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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.

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“…Both and E B decrease from 400°C, and N db increases above the same temperature. The sharp increase of the leakage current above 500°C is due to the effusion of hydrogen molecules from near Si-H groups, that initiates the decrease of the content of bonded hydrogen 43 Si-HϩSi-H→H 2 ↑ϩSi-Si. ͑2͒…”

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Temperature effects on the electrical properties and structure of interfacial and bulk defects in Al/SiNx:H/Si devices

Martínez

Andrés

Prado

et al. 2001

Journal of Applied Physics

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Bulk properties of SiN x :H thin film dielectrics and interface characteristics of SiN x :H/Si devices are studied by a combination of electrical measurements ͑capacitance-voltage and current-voltage characteristics͒ and defect spectroscopy ͑electron spin resonance͒. The SiN x :H films were deposited by an electron cyclotron resonance plasma method and subjected to rapid thermal annealing postdeposition treatments at temperatures between 300 and 1050°C for 30 s. It is found that the response of the dielectric to the thermal treatments is strongly affected by its nitrogen to silicon ratio (N/Siϭx) being above or below the percolation threshold of the Si-Si bonds in the SiN x :H lattice, and by the amount and distribution of the hydrogen content. The density of Si dangling bond defects decreases at moderate annealing temperatures ͑below 600°C͒ in one order of magnitude for the compositions above the percolation threshold ͑nitrogen rich, xϭ1.55, and near stoichiometric, x ϭ1.43͒. For the nitrogen rich films, a good correlation exists between the Si dangling bond density and the interface trap density, obtained from the capacitance measurements. This suggests that the observed behavior is mainly determined by the removal of states from the band tails associated to Si-Si weak bonds, because of the thermal relaxation of the bonding strain. At higher annealing temperatures the deterioration of the electrical properties and the increase of the Si dangling bonds seem to be associated with a release of trapped hydrogen from microvoids of the structure. For the silicon rich samples rigidity percolates in the network resulting in a rigid and strained structure for which the degradation phenomena starts at lower temperatures than for the other two types of samples.

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Hydrogen-effusion-induced structural changes and defects ina-Si:H films: Dependence upon the film microstructure

Cited by 50 publications

References 22 publications

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

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

Temperature effects on the electrical properties and structure of interfacial and bulk defects in Al/SiNx:H/Si devices

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