Eugenia Mytilineou | University of Patras (original) (raw)
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Papers by Eugenia Mytilineou
Journal of Applied Physics, 1994
The variation of a-Si:H film quality, deposited by a rf glow discharge of pure silane, is examine... more The variation of a-Si:H film quality, deposited by a rf glow discharge of pure silane, is examined as a function of the interelectrode distance for two different pressures. Constant photocurrent and modulated photocurrent methods are used to estimate the magnitude and the shape of the defect states in the valence band and the conduction band, respectively. An effort is made to correlate the film quality parameters and the defect formation with the plasma macroscopic and microscopic parameters. The results suggest that, at low interelectrode distances, high sticking coefficient radicals modify the film growth and the defect formation mechanisms, leading to the deterioration of the film quality. The conclusions drawn are compared with the predictions of recent theoretical models concerning the defect formation in a-Si:H.
Journal of Non-Crystalline Solids, 1998
In this work, results obtained from muon implantation studies on a-Ge:H, prepared by radio-freque... more In this work, results obtained from muon implantation studies on a-Ge:H, prepared by radio-frequency sputtering in an Ž. argonrhydrogen mixture at room temperature, are compared with those obtained for polycrystalline pcr Ge. Repolarization data on pcr Ge show that the majority of muons are initially trapped in isotropic tetrahedral sites. In the amorphous films, an anisotropic configuration seems to be favoured. It is possible that stretched bonds, pre-existing in the amorphous network, facilitate the formation of bond-centre sites, a suggestion that we also made for a-Si in earlier work. A higher fraction of diamagnetic centres is found in a-Ge:H compared to per Ge, probably due to muons attached to the residual dangling bonds.
Journal of Non-Crystalline Solids, 1980
ABSTRACT
Journal of Applied Physics, 1989
The aim of the present work is to optimize a well-known plasmon-based aluminum/porous anodic alum... more The aim of the present work is to optimize a well-known plasmon-based aluminum/porous anodic alumina sensor. This kind of sensors is produced by partial electrochemical anodization of an aluminum film, while the remaining, non-anodized metallic film is used for supporting the propagation of surface plasmons. The anodized porous alumina is preferable against a flat solid surface as it presents much larger sensing area and thus enhanced detecting efficiency. In this work, a novel method for controlling the remaining aluminum film thickness is reported, based on a simple optical reflectance measurement during the electrochemical anodization of the initial metallic film.
Solid State Phenomena, 1995
Philosophical Magazine, 2008
Philosophical Magazine B: Physics of Condensed Matter
ABSTRACT
The incorporation of high concentrations of different additives in the amorphous chalcogenide sem... more The incorporation of high concentrations of different additives in the amorphous chalcogenide semiconductors can affect drastically their electronic properties. The effect is known as 'modification', but sometimes is called 'doping', which could be misleading. This paper reviews some of the more important aspects of the development of the field and attempts to bring up some points that may need more attention.
Journal of Optoelectronics and Advanced Materials
The optical and the electrical properties of amorphous selenium, a-Se, and amorphous selenium con... more The optical and the electrical properties of amorphous selenium, a-Se, and amorphous selenium containing silver, a-Se 100-x Ag x , with x<5, or silver iodine, Se 100-x (AgI) x and Se 100-2x Ag x I x , with x≤15, were studied in order to determine the influence of each additive on the density of defect states in a-Se. Our results show that the addition of Ag or of AgI does not induce any impurity bands in the gap of a-Se. In some of the a-Se 1-x Ag x compositions an additional sharp peak appears at 1.9 eV. This peak has been related to accidental oxygen contamination of the particular samples and not to Ag related states. The optical gap decreases by 0.1eV with the addition of 5 at. % Ag or with 15 at. % AgI into the a-Se matrix. The spectral dependence of the photoconductivity shows a peak at 2.4 eV, which is attributed to band-to-band optical transitions. The spectral dependence of the absorption coefficient is compared to the dc photoconductivity per incident photon flux.
Journal of Non-Crystalline Solids
ABSTRACT A detailed study of the defect distribution in Ge25Se75−xBix sputtered films is presente... more ABSTRACT A detailed study of the defect distribution in Ge25Se75−xBix sputtered films is presented by means of the modulated photocurrent and the constant photocurrent methods. The combination of these techniques provides an estimate of the defect distribution within the energy gap, as each of them measures the defect concentrations in different energy regions. The addition of Bi causes an increase of the defect density of states (DOS) at the valence band (VB) side which is accompanied by a simultaneous decrease of the DOS at the conduction band (CB) side; as a result, the Fermi level shifts towards the CB and the sign of the majority carriers changes from positive to negative.
Journal of Applied Physics, 2015
MRS Proceedings, 1992
ABSTRACTWe report on evidence that fluorine, properly incorporated into a-Si, replaces weakly bon... more ABSTRACTWe report on evidence that fluorine, properly incorporated into a-Si, replaces weakly bonded hydrogen and improves the material stability under light soaking. Our fluorinated amorphous silicon (a-Si:H:F) is made by if glow discharge at high deposition temperatures up to 430 C from a gas mixture of SiH4 or Si2H6 and F2. These a-Si:H:F films show much lower density of states in the light soaking saturated state than device quality a-Si:H prepared in the same deposition system. It is evident from our results that fluorine incorporated into the network at such high deposition temperature makes for a new configuration which minimizes dangling bonds and other defects.
Photo-Induced Metastability in Amorphous Semiconductors, 2003
Journal of Applied Physics, 1994
The variation of a-Si:H film quality, deposited by a rf glow discharge of pure silane, is examine... more The variation of a-Si:H film quality, deposited by a rf glow discharge of pure silane, is examined as a function of the interelectrode distance for two different pressures. Constant photocurrent and modulated photocurrent methods are used to estimate the magnitude and the shape of the defect states in the valence band and the conduction band, respectively. An effort is made to correlate the film quality parameters and the defect formation with the plasma macroscopic and microscopic parameters. The results suggest that, at low interelectrode distances, high sticking coefficient radicals modify the film growth and the defect formation mechanisms, leading to the deterioration of the film quality. The conclusions drawn are compared with the predictions of recent theoretical models concerning the defect formation in a-Si:H.
Journal of Non-Crystalline Solids, 1998
In this work, results obtained from muon implantation studies on a-Ge:H, prepared by radio-freque... more In this work, results obtained from muon implantation studies on a-Ge:H, prepared by radio-frequency sputtering in an Ž. argonrhydrogen mixture at room temperature, are compared with those obtained for polycrystalline pcr Ge. Repolarization data on pcr Ge show that the majority of muons are initially trapped in isotropic tetrahedral sites. In the amorphous films, an anisotropic configuration seems to be favoured. It is possible that stretched bonds, pre-existing in the amorphous network, facilitate the formation of bond-centre sites, a suggestion that we also made for a-Si in earlier work. A higher fraction of diamagnetic centres is found in a-Ge:H compared to per Ge, probably due to muons attached to the residual dangling bonds.
Journal of Non-Crystalline Solids, 1980
ABSTRACT
Journal of Applied Physics, 1989
The aim of the present work is to optimize a well-known plasmon-based aluminum/porous anodic alum... more The aim of the present work is to optimize a well-known plasmon-based aluminum/porous anodic alumina sensor. This kind of sensors is produced by partial electrochemical anodization of an aluminum film, while the remaining, non-anodized metallic film is used for supporting the propagation of surface plasmons. The anodized porous alumina is preferable against a flat solid surface as it presents much larger sensing area and thus enhanced detecting efficiency. In this work, a novel method for controlling the remaining aluminum film thickness is reported, based on a simple optical reflectance measurement during the electrochemical anodization of the initial metallic film.
Solid State Phenomena, 1995
Philosophical Magazine, 2008
Philosophical Magazine B: Physics of Condensed Matter
ABSTRACT
The incorporation of high concentrations of different additives in the amorphous chalcogenide sem... more The incorporation of high concentrations of different additives in the amorphous chalcogenide semiconductors can affect drastically their electronic properties. The effect is known as 'modification', but sometimes is called 'doping', which could be misleading. This paper reviews some of the more important aspects of the development of the field and attempts to bring up some points that may need more attention.
Journal of Optoelectronics and Advanced Materials
The optical and the electrical properties of amorphous selenium, a-Se, and amorphous selenium con... more The optical and the electrical properties of amorphous selenium, a-Se, and amorphous selenium containing silver, a-Se 100-x Ag x , with x<5, or silver iodine, Se 100-x (AgI) x and Se 100-2x Ag x I x , with x≤15, were studied in order to determine the influence of each additive on the density of defect states in a-Se. Our results show that the addition of Ag or of AgI does not induce any impurity bands in the gap of a-Se. In some of the a-Se 1-x Ag x compositions an additional sharp peak appears at 1.9 eV. This peak has been related to accidental oxygen contamination of the particular samples and not to Ag related states. The optical gap decreases by 0.1eV with the addition of 5 at. % Ag or with 15 at. % AgI into the a-Se matrix. The spectral dependence of the photoconductivity shows a peak at 2.4 eV, which is attributed to band-to-band optical transitions. The spectral dependence of the absorption coefficient is compared to the dc photoconductivity per incident photon flux.
Journal of Non-Crystalline Solids
ABSTRACT A detailed study of the defect distribution in Ge25Se75−xBix sputtered films is presente... more ABSTRACT A detailed study of the defect distribution in Ge25Se75−xBix sputtered films is presented by means of the modulated photocurrent and the constant photocurrent methods. The combination of these techniques provides an estimate of the defect distribution within the energy gap, as each of them measures the defect concentrations in different energy regions. The addition of Bi causes an increase of the defect density of states (DOS) at the valence band (VB) side which is accompanied by a simultaneous decrease of the DOS at the conduction band (CB) side; as a result, the Fermi level shifts towards the CB and the sign of the majority carriers changes from positive to negative.
Journal of Applied Physics, 2015
MRS Proceedings, 1992
ABSTRACTWe report on evidence that fluorine, properly incorporated into a-Si, replaces weakly bon... more ABSTRACTWe report on evidence that fluorine, properly incorporated into a-Si, replaces weakly bonded hydrogen and improves the material stability under light soaking. Our fluorinated amorphous silicon (a-Si:H:F) is made by if glow discharge at high deposition temperatures up to 430 C from a gas mixture of SiH4 or Si2H6 and F2. These a-Si:H:F films show much lower density of states in the light soaking saturated state than device quality a-Si:H prepared in the same deposition system. It is evident from our results that fluorine incorporated into the network at such high deposition temperature makes for a new configuration which minimizes dangling bonds and other defects.
Photo-Induced Metastability in Amorphous Semiconductors, 2003