Instability effects on the dark conductivity (σDark) and photoconductivity (σphoto) of microcrystalline silicon films with different microstructures deposited on smooth and rough substrates, after exposure to different storage conditions have been investigated. Samples stored in vacuum are less affected by aging than films stored in air and sealed plastic bags filled with N2 gas. The aging is reversible after annealing at 450 K. Thin films deposited on smooth and rough substrates with the same thickness and silane concentrations (SC) during the same deposition run showed similar aging effects. Thick samples exhibited a decrease in σDark, while both decrease and increase in σDark occur in thin samples after aging. For each sample, σDark and σphoto presented the same type of aging, independent of thickness and type of substrate used. The applicability of the steady‐state photocarrier grating technique was successfully tested on the rough substrates. Light‐induced degradation studies confirm the dependence of the Staebler‐Wronski effect on the crystallinity of the material (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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Previous studies indicate that the dark conductivity in amorphous and microcrystalline silicon may increase or decrease with exposure to deionized water (DIW) or pure oxygen at 80 °C but always decreases with light exposure. While the light-induced effect is linked to paramagnetic dangling bonds (Do), the origin of metastability in microcrystalline silicon remains unclear. In this study, we use steady-state photoconductivity (SSPC), dual-beam photoconductivity (DBP), and electron spin resonance (ESR), to study the behaviors under soaking in DIW and (or) pure oxygen at 80 °C and light-exposure of amorphous (a-Si:H) and nanostructured (nc-Si:H) silicon samples deposited in a capacitively coupled plasma-enhanced chemical vapor deposition system. Powders from thick samples of low and high crystallinity (Xc) peeling off large substrates were collected in quartz tubes for ESR measurements. Dark conductivity decreases upon exposure to pure oxygen at 80 °C for nc-Si:H but remains unchanged for a-Si:H. The ESR signal attributed to Do decreases with soaking in DIW for high and low crystallinity nc-Si:H but the effect is more significant for higher Xc. Changes in SSPC, DBP, and ESR are used to compare the degradation mechanisms because of O2 exposure and light for amorphous and nanostructured silicon.

Methylammonium lead iodide (MAPbI$$_3$$ 3 ) (CH$$_3$$ 3 NH$$_3$$ 3 PbI$$_3$$ 3 ) is popular material for edge technology application, but it still includes many uncertainties. Particularly, molecular and electronic degradation (electronic defect distribution) and mobility–lifetime product still hold many mysteries. Stemming from the atmospheric or light-induced degradation, mobility–lifetime product changes are still unknown and haven’t been studied up to now. In this study, mobility–lifetime product change was investigated depending on degradation source such as atmospheric and light soaked. MAPbI$$_3$$ 3 films were deposited by thermal chemical vapor deposition (thermal CVD). Structural analysis was done by X-ray diffraction (XRD), respectively. Deposited MAPbI$$_3$$ 3 films were exposed to laboratory ambient, vacuum atmosphere, deionized water vapor (DIWV) atmosphere and UV light soaking at constant temperature (300K) to define changes on mobility–lifetime product.

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Metastability effects in hydrogenated microcrystalline silicon thin films due to air, high purity nitrogen, helium, argon, and oxygen were investigated using temperature-dependent dark conductivity, photoconductivity, and steady-state photocarrier grating methods. It was found that short-term air, nitrogen, and inert gases caused a small reversible increase of σDark and σphoto within a factor of two, but they did not affect the minority carrier μτ-products significantly. These changes are partially reduced by vacuum treatment and completely reduced after heat treatment at 430 K. However, oxygen gas treatment at 80 °C resulted in more than an order of magnitude increase in both σDark and σphoto and an increase in the diffusion length, LD, by 50% from that of the annealed-state value in highly crystalline samples, while no significant metastability is detected in amorphous and low crystalline silicon thin films. A following heat treatment partially recovers both σDark and σphoto to their annealed-state values, while LD decreases only slightly. Such increase in the LD values could be due to a decrease in the density of recombination centers for holes below the Fermi level, which may be related to passivation of defects by oxygen on the surface of crystalline grains.

Metastability and instability effects due to oxygen exposure in thick intrinsic hydrogenated microcrystalline silicon films deposited by very high frequency plasma enhanced chemical vapour deposition on smooth glass substrates were investigated using temperature-dependent dark conductivity, steady state photoconductivity, and sub-bandgap absorption measurements obtained using the dual beam photoconductivity (DBP) method. No significant changes in dark conductivity and photoconductivity were detected even after long-term air exposure of samples in room ambient as well as after oxygen exposure when samples were characterized in oxygen ambient. However, characterization of the oxygen-exposed state in high vacuum caused an increase in dark conductivity and photoconductivity as well as a significant decrease in the sub-bandgap absorption coefficient spectra in the low energy region in samples with I C RS Ͼ 0.40. These changes are partially irreversible for samples I C RS Ͼ 0.80 and mostly reversible for compact materials with significant amorphous fraction. No detectable metastable changes occurred in microcrystalline silicon samples with I C RS Ͻ 0.40 as well as in pure amorphous silicon.Résumé : Nous utilisons la conductivité en obscurité, la photoconductivité stationnaire et des mesures d'absorption sous la bande interdite obtenues de la méthode de photoconductivité à deux faisceaux (DBP), afin d'étudier les effets stables et métastables de l'exposition à l'oxygène de films de silicium microcristallins hydrogénés épais déposés par plasma à haute fréquence augmenté d'un dépôt de vapeur chimique sur un substrat de verre lisse. Nous ne détectons aucun changement de la conductivité en obscurité ni de la photoconductivité, même après une longue exposition à l'air à température ambiante, aussi bien qu'après exposition à l'oxygène où les échantillons sont examinés dans une atmosphère d'oxygène. Cependant, étudier sous vide les échantillons exposés à l'oxygène donne une augmentation de la conductivité en obscurité, aussi bien que de la photoconductivité, en même temps qu'une diminution significative de l'absorption sous la bande interdite dans les échantillons avec I C RS Ͼ 0.40. Ces changements sont partiellement réversibles pour les échantillons avec I C RS Ͼ 0.80 et majoritairement réversibles pour les matériaux compacts avec une fraction amorphe importante. Nous ne détectons aucun changement méta-stable dans les échantillons de silicium microcristallin avec I C RS Ͻ 0.40 ni dans le silicium complètement amorphe. [Traduit par la Rédaction]

The reactive ion etching (RIE) of the binary transition-metal oxides (TMOs) NiO, CuO and CoO, which are expected to be key materials of resistance random access memory (RRAMÔ), was investigated. We found that inductively coupled plasma using CHF 3 -based discharge, which is highly compatible with conventional semiconductor RIE, is effective for the TMOs studied here. Furthermore, device fabrication using Pt/CoO/Pt trilayers is carried out, and a large change in resistance, which is an essential functionality of RRAM, was successfully observed. This should be definite evidence of a successful RIE realized in the present device fabrication.