Metastability effects in hydrogenated microcrystalline silicon thin films investigated by the dual beam photoconductivity method

Güneş, Mehmet; Cansever, Hamza; Yilmaz, Gökhan; Smirnov, Vladimir; Finger, F.; Brüggemann, R.

doi:10.1016/j.jnoncrysol.2012.01.063

Cited by 13 publications

(14 citation statements)

References 16 publications

(30 reference statements)

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“…4 is a reduction of spectrum below 1.3 eV after adsorption compared with one after annealing. Fig.5 is another result for a film with a thickness of 1.28 ,m. A similar result was reported by Gunes et al [8]. They used the dual beam photoconductivity method to measure sub-gap optical absorption for µc-Si:H films with thickness between 200 nm and 350 nm.…”

Section: Resultssupporting

confidence: 79%

“…The positive Fermi level shift and the dark conductivity decrease in atmospheric adsorption of µc-Si:H may correspond to the positive threshold voltage shift and the drain current decrease in positive bias-stress induced instabilities in a-Si:H TFTs, respectively. Furthermore, the same resultswere observed for the CPM spectra in µc-Si:H and a-Si:H TFTs with a built-in upward band-bending [8,12,13].Furthermore, dark conductivity increase and negative Fermi level shift in atmospheric adsorption of µc-Si:H may correspond to the drain current increase and the negative threshold voltage shift in negative bias-stress induced instabilities in a-Si:H TFTs. In TFTs, Negative bias-stress makes downward built-in band-bending due to the trapped holes within gate insulator.…”

Section: Discussionsupporting

confidence: 77%

“…By atmospheric adsorption, the dark conductivity can be either decreased or increased. It has been postulated that the decrease (increase) is related to the electron acceptor (donor) such as oxygen (water) molecules adsorbed on the surface of the film, within cracks or at grain boundaries [1][2][3][4][5][6][7][8]. The adsorption ofelectron acceptor (donor) molecules will create upward (downward) band-bending and thereby establish depletion (accumulation) layer at the surface, which will result in a decrease (increase) in conductivity.…”

Section: Resultsmentioning

confidence: 99%

“…For some µc-Si:H films, decreases up to several orders of magnitude during the storage of films in the air, of which initial value may be restored by annealing in vacuum at around 200℃. The annealed value may remain stable when the film is kept in vacuum, whereas it changes again when put back into the air [1][2][3][4][5][6][7][8].…”

Section: Introductionmentioning

confidence: 99%

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New Findings and Interpretation on Atmospheric Adsorption Induced Instability in Microcrystalline Silicon Films

Lim

Park

2014

IJMSA

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Abstract:In this investigation, we added some new findings and interpretations on the behaviors of both electrical conductivities and optical absorption spectra upon adsorption of atmospheric molecules in microcrystalline silicon films (µc-Si:H). The photo conductivity followed similar decay-recover processes upon air exposure-thermal anneal cycles as did the dark conductivity. The dark and photo conductivities decay according to a stretched-exponential function with time upon air exposure. The absorption spectra showed a reduced defect absorption for the films at air exposed state compared with those of at thermal annealed state. There is a one-to-one correspondence between atmospheric adsorption in µc-Si:H and bias-stress induced instabilities in a-Si:H thin film transistors(TFTs).

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Section: Resultssupporting

confidence: 79%

Section: Discussionsupporting

confidence: 77%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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New Findings and Interpretation on Atmospheric Adsorption Induced Instability in Microcrystalline Silicon Films

Lim

Park

2014

IJMSA

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“…It was shown that majority carrier -products can be affected by the air exposure and heat treatment of the samples, accompanying the corresponding changes in dark while the minority carrier -products obtained from the SSPG measurements were found to be insensitive to the changes in dark , suggesting such changes occurred only due to Fermi level shift obeying to the Meyer-Neldel rule [5]. It was recently reported that pure oxygen and deionized (DI) water treatment increased dark and photo irreversibly by a few orders [13]. These changes correlate well with permanent shift of dark Fermi level towards the conduction band edge, which will eventually increase the density of occupied defect states below the Fermi level.…”

Section: Introductionmentioning

confidence: 97%

Investigation of meta- and in-stability effects in hydrogenated microcrystalline silicon thin films by the steady-state measurement methods

et al. 2014

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Metastability effects because of atmospheric exposure, high purity gasses, and deionized water in hydrogenated microcrystalline silicon thin films with different crystalline volume fractions were studied using well accepted steady-state characterization methods of dark conductivity, steady-state photoconductivity, steady-state photocarrier grating (SSPG) and dual beam photoconductivity (DBP) methods. A standard measurement procedure has been established before using the steady state methods, in which a steady state condition of dark conductivity was established by monitoring the time dependence of dark conductivity. Samples deposited on smooth glass and rough glass substrates exhibit similar reversible and irreversible changes in the properties of microcrystalline silicon film. A reliable correlation of reversible and irreversible changes indicate that dark conductivity and photoconductivity values increase, sub-bandgap absorption spectrum obtained from DBP method decrease and correspondingly minority carrier diffusion lengths obtained from the SSPG method increase in the metastable state in various amount for microcrystalline films with crystalline volume fraction, I C RS > 0.30. Amorphous silicon and microcrystalline silicon films with I C RS < 0.30 do not show detectable metastable changes as samples exposed to atmospheric condition as well as high purity oxygen gas and deionized water.Résumé : Nous utilisons des méthodes de caractérisation stationnaire bien acceptées, comme la conductivité en obscurité, la photoconductivité stationnaire, la photoconductivité stationnaire par interférométrie laser (SSPG) et la photoconductivité modulée à deux faisceaux (DBP), afin d'étudier l'effet de la métastabilité dans des films minces de silicium microcristallin hydrogénés, suite à l'exposition à l'atmosphère, aux gaz de haute pureté et à l'eau dé-ionisé. Avant d'utiliser ces méthodes stationnaires, nous avons développé une procédure standard de mesure, dans laquelle la condition stationnaire de conductivité en obscurité est vérifiée en observant la dépendance en temps de la conductivité en obscurité. Les échantillons déposés sur des surfaces douces et rudes de substrats de verre montrent les mêmes changements réversibles et irréversibles dans les propriétés microcristallines des films de silicium. Une corrélation fiable des changements réversibles et irréversibles des propriétés des films microcristallins indique que les valeurs de conductivité en obscurité et de photoconductivité augmentent et que le spectre d'absorption sous la bande interdite obtenu de SSPG augmente dans les films microcristallins en état métastable pour lesquels la fraction cristalline en volume I C RS > 0.3. Les films de silicium amorphes et microcristallins avec I C RS < 0.3 ne montrent aucun changement métastable détectable lorsque les échantillons sont exposés aux conditions atmosphériques, à l'oxygène pur et à l'eau dé-ionisée. [Traduit par la Rédaction]

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Microstructure and carrier‐transport behaviors of nanocrystalline silicon thin films annealed at various temperatures

Shan

et al. 2016

Physica Status Solidi (a)

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Hydrogenated amorphous Si films were prepared by a plasma‐enhanced chemical vapor deposition technique. As‐deposited samples were then thermally annealed at various temperatures to obtain nanocrystalline silicon films. The microstructures and carrier‐transport characteristics were investigated during the transition process from amorphous to nanocrystalline phase. It was found that the Hall mobility was improved while the dark conductivity was increased by over two orders of magnitude after annealing. Temperature‐dependent Hall measurements were performed in the temperature range from 310 to 575 K. Hall mobility first increases with rising temperature to 400 K and then decreases with further increasing temperature. The different temperature dependence of Hall mobility shows that the microscopic mechanisms governing charge transport are different for nanocrystalline Si films in different temperature regions.

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Metastability effects in hydrogenated microcrystalline silicon thin films investigated by the dual beam photoconductivity method

Cited by 13 publications

References 16 publications

New Findings and Interpretation on Atmospheric Adsorption Induced Instability in Microcrystalline Silicon Films

New Findings and Interpretation on Atmospheric Adsorption Induced Instability in Microcrystalline Silicon Films

Investigation of meta- and in-stability effects in hydrogenated microcrystalline silicon thin films by the steady-state measurement methods

Microstructure and carrier‐transport behaviors of nanocrystalline silicon thin films annealed at various temperatures

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