Nikolaos Spiliopoulos | University of Patras (original) (raw)

Papers by Nikolaos Spiliopoulos

Research paper thumbnail of Comparison of different methods for the measurements and calculations of Capacitively Coupled Plasmas electrical characteristics

Bulletin of the American Physical Society, Oct 12, 2016

Submitted for the GEC16 Meeting of The American Physical Society Comparison of different methods ... more Submitted for the GEC16 Meeting of The American Physical Society Comparison of different methods for the measurements and calculations of Capacitively Coupled Plasmas electrical characteristics GIAN

Research paper thumbnail of Influence of plasma conditions on the defect formation mechanism in amorphous hydrogenated silicon

Journal of Applied Physics, Feb 1, 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.

Research paper thumbnail of Specific Problems of Rotational Temperature Determination in Plasmas of Molecular Gases

Research paper thumbnail of Complexation of Lysozyme with Adsorbed PtBS-<i>b</i>-SCPI Block Polyelectrolyte Micelles on Silver Surface

Langmuir, Jan 6, 2015

We present a study of the interaction of the positively charged model protein lysozyme with the n... more We present a study of the interaction of the positively charged model protein lysozyme with the negatively charged amphiphilic diblock polyelectrolyte micelles of poly(tert-butylstyrene)-bsodium (sulfamate/carboxylate)isoprene) (PtBS-b-SCPI) on the surface of silver. The adsorption kinetics are monitored by surface plasmon resonance and the surface morphology by atomic force microscopy. The micellar adsorption kinetics is dictated by two processes and the micellar layer morphology shows that the micelles do not lose their integrity upon adsorption. The complexation of lysozyme with the adsorbed micellar layers depends on the micelles arrangement and density in the underlying layer and lysozyme follows the local morphology of the underlying roughness. When the micellar adsorbed amount is small, the layers show low capacity in protein binding and low resistance in loading. When the micellar adsorbed amount is high the situation is inversed. The adsorbed layers both with or without added protein are found to be irreversibly adsorbed on the Ag surface.

Research paper thumbnail of Plasma Impedance in Discharges

CRC Press eBooks, Dec 12, 2016

Research paper thumbnail of Influence of Discharge Geometry on Power Dissipation and Sheath Impedances in Silane Discharges

Japanese Journal of Applied Physics, Jul 1, 1997

Research paper thumbnail of Disilane addition versus silane-hydrogen flow rate effect on the PECVD of silicon thin films

Journal of vacuum science & technology, Nov 1, 2016

The effect of small disilane addition to the silane/hydrogen mixture and of the total silane/hydr... more The effect of small disilane addition to the silane/hydrogen mixture and of the total silane/hydrogen flow rate on the silicon thin film growth rate and crystallinity were investigated. The study was performed by using simplified gas phase chemistry model along with plasma diagnostics such as electrical and deposition rate measurements. The results showed that even small disilane addition induces an increase in the electron density, silane electron-induced dissociation rate, and film growth rate. The increase in the total flow rate caused a linear increase in the film growth rate despite the negligible effect on the discharge microscopic parameters. Similar deposition rates and crystallinities were achieved with both disilane addition and increase in the flow rate, but the deposition efficiency was much higher in the case of disilane addition. The simplified gas phase chemistry model indicated an increase in the silyl production rate either with the disilane addition or the increase in the flow rate. Almost the same silyl production rates were calculated for both parameters, but for the disilane addition case, this was achieved with much less silicon containing molecules in the gas feed. Finally, the increase in the silyl production rate combined to the almost constant hydrogen atoms production, and consumption rate is estimated as the main reason for the drop in the crystallinity with the increase in disilane fraction in the mixture or the total flow rate. V

Research paper thumbnail of Usage of Si2H6 for Si Tf PECVD at Enhanced Deposition Rate

World Conference on Photovoltaic Energy Conversion, Oct 10, 2011

The effect of very small disilane addition in silane-hydrogen mixtures on the growth rate of sili... more The effect of very small disilane addition in silane-hydrogen mixtures on the growth rate of silicon thin films is investigated. Different ways of gas introduction into the plasma zone were tested including single gas entrance configuration as well as two different showerhead designs. Variation of flow and mixing conditions were critical for the effect of disilane addition on the electrical properties of the discharge and the film growth rate. Electrical measurements showed that the power density of the discharge is slightly affected by the disilane addition but affects much stronger the phase impedance leading to more resistive plasmas. The way the growth rate is influenced by the disilane addition depends on the RF electrode design and the proper choice of the process parameters.

Research paper thumbnail of Disilane as a growth rate catalyst of plasma deposited microcrystalline silicon thin films

AIP Advances, Jul 1, 2016

A model for the discharge kinetics and plasma chemistry during plasma enhanced chemical vapor dep... more A model for the discharge kinetics and plasma chemistry during plasma enhanced chemical vapor deposition of amorphous silicon

Research paper thumbnail of Arrhenius-like behavior in plasma reactions

Applied Physics Letters, Aug 4, 1997

Research paper thumbnail of Reflection and transmission coefficients of nano-metamaterial antennas at microwave frequencies

ABSTRACT The hypothesis of this paper is that when metallic nanoparticles are grouped together by... more ABSTRACT The hypothesis of this paper is that when metallic nanoparticles are grouped together by suitable field coupling they can behave like larger objects which will resonate at microwave frequencies. This means that sheets of nanomaterials can be designed that are largely transparent at these spectra except where an antenna has been created from densely grouped clusters of metallic nanoparticles. Simulations, based on actual samples composed of nano-metamaterials, show the behaviour of the reflection and transmission coefficients of antennas. The reso-nant frequency can increase or decrease depending on the geometry.

Research paper thumbnail of Flow through Alumina Nanopores Bearing Responsive Polymer Brushes

Research paper thumbnail of Accurate rf Discharge Characterization and Influence of Reactor System Design on the Microscopic Plasma Parameters

Plasma processing is widely used in various applications covering the deposition of thin films, s... more Plasma processing is widely used in various applications covering the deposition of thin films, surface modification, dry etching e.t.c. Although good progress has been done in the last decades in all these processes there are still open issues concerning especially the design of plasma apparatus and the effective control of plasma parameters. A good part of these issues is related to the electrical characterisation of the chamber and the subsequent measurement of the real power consumption during the process. This leads to discrepancies in the experimental results between different labs around the world which hinders the transfer of knowledge and in many cases in poor repeatability. Moreover, in most of the cases plasma reactors and associated equipment are not optimally designed for the specific process and this may result in significant economic and environmental problems. The aim of this work is to point out significant externally measured plasma parameters that could ease desig...

Research paper thumbnail of MP22-15 Stone Retropulsion with the Use of a Recently Introduced Holmium Laser System

The Journal of Urology, 2016

In our investigation, increased operative time of PCNL procedures was not associated with an incr... more In our investigation, increased operative time of PCNL procedures was not associated with an increase in complications. The increase in mid-level complications observed in patients identified to have infection-based stones corroborates previous data on this particular group of stone patients. While, in general, it is advisable to minimize operative duration, this data does not suggest an increased complication risk with lengthier PCNL procedures.

Research paper thumbnail of Solar Energy Materials and Systems for an Aesthetic and Sustainable Future

Contemporary Materials, 2014

Renewable energy sources have an important role in global energy demand in the 21st century. New ... more Renewable energy sources have an important role in global energy demand in the 21st century. New investigations in solar energy materials and solar energy systems offer new opportunities for a sustainable future, adapting local energy needs, environmental protection and aesthetics. Solar energy can be used almost everywhere, with visible materials and systems. In this paper, an overview of new solar energy materials and systems is presented, focused on the work that is performed in the Laboratories of the University of Patras and of the Technical Educational Institute. The research activities of these Laboratories are on nanotechnology, biotechnology, microalgae hydrogen production, photovoltaics, smart glazings and materials for solar energy systems. A brief description of the achieved improvements on these solar energy materials is included, where energy performance and system cost play an important role together with aesthetics, considering their wide application in the future.

Research paper thumbnail of Comparison of different methods for the measurements and calculations of Capacitively Coupled Plasmas electrical characteristics

Bulletin of the American Physical Society, 2016

Research paper thumbnail of Usage of Si2H6 for Si Tf PECVD at Enhanced Deposition Rate

The effect of very small disilane addition in silane-hydrogen mixtures on the growth rate of sili... more The effect of very small disilane addition in silane-hydrogen mixtures on the growth rate of silicon thin films is investigated. Different ways of gas introduction into the plasma zone were tested including single gas entrance configuration as well as two different showerhead designs. Variation of flow and mixing conditions were critical for the effect of disilane addition on the electrical properties of the discharge and the film growth rate. Electrical measurements showed that the power density of the discharge is slightly affected by the disilane addition but affects much stronger the phase impedance leading to more resistive plasmas. The way the growth rate is influenced by the disilane addition depends on the RF electrode design and the proper choice of the process parameters.

Research paper thumbnail of Surface plasmon resonance study of adhesion kinetics of smectites on the Au/water interface: Clay and organo-clay film formation

Applied Clay Science, 2019

Abstract Surface plasmon resonance was employed for the in-situ investigation of film formation f... more Abstract Surface plasmon resonance was employed for the in-situ investigation of film formation from aqueous dispersions of clay minerals on gold/water interface. High charge (SAz-1) and intermediate charge smectite (STx-1b) were studied for their ability to form stable clay films on gold surfaces and their adhesion kinetics at different concentrations was investigated. Layer charge and charge distribution seems to affect not only the kinetics of film formation but also the overall amount of clay mineral on the gold substrate. Subsequently to stable clay mineral film formation, the in-situ preparation of hybrid organo-clay films with the introduction of alkylammonium chains and their adsorption kinetics was examined. Alkylammonium adsorption via ion exchange in the interlayer of the clay minerals is controlled by the density of the clay mineral film in full accordance with layer charge and charge localization. Hence, a simple self-assembly procedure for the in-situ preparation of hybrid organo-clay films for novel applications is proposed.

Research paper thumbnail of Disilane addition versus silane-hydrogen flow rate effect on the PECVD of silicon thin films

Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, 2016

Research paper thumbnail of Formation of alkane-phosphonic acid self-assembled monolayers on alumina: an in situ SPR study

Surface and Interface Analysis, 2009

Abstract The formation process of n-alkane phosphonic acid CH 3 (CH 2) n− 1 PO (OH) 2 (n= 10, 12,... more Abstract The formation process of n-alkane phosphonic acid CH 3 (CH 2) n− 1 PO (OH) 2 (n= 10, 12, 14, 18) self-assembled monolayers (SAMs), deposited from ethanol solutions on aluminum oxide, has been monitored in situ using surface plasmon resonance (SPR) ...

Research paper thumbnail of Comparison of different methods for the measurements and calculations of Capacitively Coupled Plasmas electrical characteristics

Bulletin of the American Physical Society, Oct 12, 2016

Submitted for the GEC16 Meeting of The American Physical Society Comparison of different methods ... more Submitted for the GEC16 Meeting of The American Physical Society Comparison of different methods for the measurements and calculations of Capacitively Coupled Plasmas electrical characteristics GIAN

Research paper thumbnail of Influence of plasma conditions on the defect formation mechanism in amorphous hydrogenated silicon

Journal of Applied Physics, Feb 1, 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.

Research paper thumbnail of Specific Problems of Rotational Temperature Determination in Plasmas of Molecular Gases

Research paper thumbnail of Complexation of Lysozyme with Adsorbed PtBS-<i>b</i>-SCPI Block Polyelectrolyte Micelles on Silver Surface

Langmuir, Jan 6, 2015

We present a study of the interaction of the positively charged model protein lysozyme with the n... more We present a study of the interaction of the positively charged model protein lysozyme with the negatively charged amphiphilic diblock polyelectrolyte micelles of poly(tert-butylstyrene)-bsodium (sulfamate/carboxylate)isoprene) (PtBS-b-SCPI) on the surface of silver. The adsorption kinetics are monitored by surface plasmon resonance and the surface morphology by atomic force microscopy. The micellar adsorption kinetics is dictated by two processes and the micellar layer morphology shows that the micelles do not lose their integrity upon adsorption. The complexation of lysozyme with the adsorbed micellar layers depends on the micelles arrangement and density in the underlying layer and lysozyme follows the local morphology of the underlying roughness. When the micellar adsorbed amount is small, the layers show low capacity in protein binding and low resistance in loading. When the micellar adsorbed amount is high the situation is inversed. The adsorbed layers both with or without added protein are found to be irreversibly adsorbed on the Ag surface.

Research paper thumbnail of Plasma Impedance in Discharges

CRC Press eBooks, Dec 12, 2016

Research paper thumbnail of Influence of Discharge Geometry on Power Dissipation and Sheath Impedances in Silane Discharges

Japanese Journal of Applied Physics, Jul 1, 1997

Research paper thumbnail of Disilane addition versus silane-hydrogen flow rate effect on the PECVD of silicon thin films

Journal of vacuum science & technology, Nov 1, 2016

The effect of small disilane addition to the silane/hydrogen mixture and of the total silane/hydr... more The effect of small disilane addition to the silane/hydrogen mixture and of the total silane/hydrogen flow rate on the silicon thin film growth rate and crystallinity were investigated. The study was performed by using simplified gas phase chemistry model along with plasma diagnostics such as electrical and deposition rate measurements. The results showed that even small disilane addition induces an increase in the electron density, silane electron-induced dissociation rate, and film growth rate. The increase in the total flow rate caused a linear increase in the film growth rate despite the negligible effect on the discharge microscopic parameters. Similar deposition rates and crystallinities were achieved with both disilane addition and increase in the flow rate, but the deposition efficiency was much higher in the case of disilane addition. The simplified gas phase chemistry model indicated an increase in the silyl production rate either with the disilane addition or the increase in the flow rate. Almost the same silyl production rates were calculated for both parameters, but for the disilane addition case, this was achieved with much less silicon containing molecules in the gas feed. Finally, the increase in the silyl production rate combined to the almost constant hydrogen atoms production, and consumption rate is estimated as the main reason for the drop in the crystallinity with the increase in disilane fraction in the mixture or the total flow rate. V

Research paper thumbnail of Usage of Si2H6 for Si Tf PECVD at Enhanced Deposition Rate

World Conference on Photovoltaic Energy Conversion, Oct 10, 2011

The effect of very small disilane addition in silane-hydrogen mixtures on the growth rate of sili... more The effect of very small disilane addition in silane-hydrogen mixtures on the growth rate of silicon thin films is investigated. Different ways of gas introduction into the plasma zone were tested including single gas entrance configuration as well as two different showerhead designs. Variation of flow and mixing conditions were critical for the effect of disilane addition on the electrical properties of the discharge and the film growth rate. Electrical measurements showed that the power density of the discharge is slightly affected by the disilane addition but affects much stronger the phase impedance leading to more resistive plasmas. The way the growth rate is influenced by the disilane addition depends on the RF electrode design and the proper choice of the process parameters.

Research paper thumbnail of Disilane as a growth rate catalyst of plasma deposited microcrystalline silicon thin films

AIP Advances, Jul 1, 2016

A model for the discharge kinetics and plasma chemistry during plasma enhanced chemical vapor dep... more A model for the discharge kinetics and plasma chemistry during plasma enhanced chemical vapor deposition of amorphous silicon

Research paper thumbnail of Arrhenius-like behavior in plasma reactions

Applied Physics Letters, Aug 4, 1997

Research paper thumbnail of Reflection and transmission coefficients of nano-metamaterial antennas at microwave frequencies

ABSTRACT The hypothesis of this paper is that when metallic nanoparticles are grouped together by... more ABSTRACT The hypothesis of this paper is that when metallic nanoparticles are grouped together by suitable field coupling they can behave like larger objects which will resonate at microwave frequencies. This means that sheets of nanomaterials can be designed that are largely transparent at these spectra except where an antenna has been created from densely grouped clusters of metallic nanoparticles. Simulations, based on actual samples composed of nano-metamaterials, show the behaviour of the reflection and transmission coefficients of antennas. The reso-nant frequency can increase or decrease depending on the geometry.

Research paper thumbnail of Flow through Alumina Nanopores Bearing Responsive Polymer Brushes

Research paper thumbnail of Accurate rf Discharge Characterization and Influence of Reactor System Design on the Microscopic Plasma Parameters

Plasma processing is widely used in various applications covering the deposition of thin films, s... more Plasma processing is widely used in various applications covering the deposition of thin films, surface modification, dry etching e.t.c. Although good progress has been done in the last decades in all these processes there are still open issues concerning especially the design of plasma apparatus and the effective control of plasma parameters. A good part of these issues is related to the electrical characterisation of the chamber and the subsequent measurement of the real power consumption during the process. This leads to discrepancies in the experimental results between different labs around the world which hinders the transfer of knowledge and in many cases in poor repeatability. Moreover, in most of the cases plasma reactors and associated equipment are not optimally designed for the specific process and this may result in significant economic and environmental problems. The aim of this work is to point out significant externally measured plasma parameters that could ease desig...

Research paper thumbnail of MP22-15 Stone Retropulsion with the Use of a Recently Introduced Holmium Laser System

The Journal of Urology, 2016

In our investigation, increased operative time of PCNL procedures was not associated with an incr... more In our investigation, increased operative time of PCNL procedures was not associated with an increase in complications. The increase in mid-level complications observed in patients identified to have infection-based stones corroborates previous data on this particular group of stone patients. While, in general, it is advisable to minimize operative duration, this data does not suggest an increased complication risk with lengthier PCNL procedures.

Research paper thumbnail of Solar Energy Materials and Systems for an Aesthetic and Sustainable Future

Contemporary Materials, 2014

Renewable energy sources have an important role in global energy demand in the 21st century. New ... more Renewable energy sources have an important role in global energy demand in the 21st century. New investigations in solar energy materials and solar energy systems offer new opportunities for a sustainable future, adapting local energy needs, environmental protection and aesthetics. Solar energy can be used almost everywhere, with visible materials and systems. In this paper, an overview of new solar energy materials and systems is presented, focused on the work that is performed in the Laboratories of the University of Patras and of the Technical Educational Institute. The research activities of these Laboratories are on nanotechnology, biotechnology, microalgae hydrogen production, photovoltaics, smart glazings and materials for solar energy systems. A brief description of the achieved improvements on these solar energy materials is included, where energy performance and system cost play an important role together with aesthetics, considering their wide application in the future.

Research paper thumbnail of Comparison of different methods for the measurements and calculations of Capacitively Coupled Plasmas electrical characteristics

Bulletin of the American Physical Society, 2016

Research paper thumbnail of Usage of Si2H6 for Si Tf PECVD at Enhanced Deposition Rate

The effect of very small disilane addition in silane-hydrogen mixtures on the growth rate of sili... more The effect of very small disilane addition in silane-hydrogen mixtures on the growth rate of silicon thin films is investigated. Different ways of gas introduction into the plasma zone were tested including single gas entrance configuration as well as two different showerhead designs. Variation of flow and mixing conditions were critical for the effect of disilane addition on the electrical properties of the discharge and the film growth rate. Electrical measurements showed that the power density of the discharge is slightly affected by the disilane addition but affects much stronger the phase impedance leading to more resistive plasmas. The way the growth rate is influenced by the disilane addition depends on the RF electrode design and the proper choice of the process parameters.

Research paper thumbnail of Surface plasmon resonance study of adhesion kinetics of smectites on the Au/water interface: Clay and organo-clay film formation

Applied Clay Science, 2019

Abstract Surface plasmon resonance was employed for the in-situ investigation of film formation f... more Abstract Surface plasmon resonance was employed for the in-situ investigation of film formation from aqueous dispersions of clay minerals on gold/water interface. High charge (SAz-1) and intermediate charge smectite (STx-1b) were studied for their ability to form stable clay films on gold surfaces and their adhesion kinetics at different concentrations was investigated. Layer charge and charge distribution seems to affect not only the kinetics of film formation but also the overall amount of clay mineral on the gold substrate. Subsequently to stable clay mineral film formation, the in-situ preparation of hybrid organo-clay films with the introduction of alkylammonium chains and their adsorption kinetics was examined. Alkylammonium adsorption via ion exchange in the interlayer of the clay minerals is controlled by the density of the clay mineral film in full accordance with layer charge and charge localization. Hence, a simple self-assembly procedure for the in-situ preparation of hybrid organo-clay films for novel applications is proposed.

Research paper thumbnail of Disilane addition versus silane-hydrogen flow rate effect on the PECVD of silicon thin films

Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, 2016

Research paper thumbnail of Formation of alkane-phosphonic acid self-assembled monolayers on alumina: an in situ SPR study

Surface and Interface Analysis, 2009

Abstract The formation process of n-alkane phosphonic acid CH 3 (CH 2) n− 1 PO (OH) 2 (n= 10, 12,... more Abstract The formation process of n-alkane phosphonic acid CH 3 (CH 2) n− 1 PO (OH) 2 (n= 10, 12, 14, 18) self-assembled monolayers (SAMs), deposited from ethanol solutions on aluminum oxide, has been monitored in situ using surface plasmon resonance (SPR) ...