Evangelos I . Dimitriadis | International Hellenic University - IHU (original) (raw)

Papers by Evangelos I . Dimitriadis

We present here an FPGA-based system, capable of simultaneous measuring and control of visible an... more We present here an FPGA-based system, capable of simultaneous measuring and control of visible and infrared lighting, temperature and humidity values of a greenhouse or industrial environment. The system uses DE10-Lite FPGA board with four sensors connected to it and in conjunction with the easy way of expanding both its software and hardware by adding more sensors, in order to cover larger areas, it is considered to be of low cost. All sensors and time values act as input. Sensors' range values and time duration for each of them are initially set by the programmer. The program used in this work converts analog inputs to digital values and displays corresponding voltage measurements in seven-segment displays of the board. A series of processes is activated upon system is set to ON, in order to achieve checking and control of parameter values. Blue LEDs and corresponding control systems are activated if related sensors' values become less than lower critical values set by programmer, while red LEDs and corresponding control systems are activated for sensors' values overcoming upper critical values. Especially for visible light values, step motor for opening or closing curtains is also activated and FPGA's board LEDs and buzzer connected to it are also ON, when upper critical value is exceeded. Yellow LEDs are activated for each parameter exceeding time set values. Finally an alarm level system turns on corresponding LEDs, depending on the number of parameter values that simultaneously exceed range values set by programmer.

A g-sensor based alarm system, available for use in many tilt sensor applications, was programmed... more A g-sensor based alarm system, available for use in many tilt sensor applications, was programmed and put in use in this work. The DE10-Lite FPGA was used, with its digital accelerometer sensor module ADXL345. The tilt sensor is programmed to present in seven segment display of the FPGA board, angle values from 0 to 90 degrees, using minus sign when the slope is to the right and the positive one when it tilts to the left, thus informing us about the sensor's tilt direction. Simultaneously the FPGA's right or left LEDs light up according to system tilt. It also uses key button for freezing its operation, hence presenting the latest angle value. The program controlling the sensor gives the ability of entering a critical angle value, depending on the application. As soon as this value is exceeded buzzer is activated, thus giving our system an alarm behavior.

Electronics Letters, 1992

(HWHM) channel separations. The LMS algorithm was initiated at iteration 300. SCR improved from 2... more (HWHM) channel separations. The LMS algorithm was initiated at iteration 300. SCR improved from 2.5 to 35 dB. The SCR using optimum weights from eqn. 2 is 37 dB. Before proceeding the performance criteria will be defined. The results of eqn. 2 are optimum and can be used as an upper bound for the performance of any cancellation algorithms. Given WO, three important quantities can be calculated. These are the expected value of the output noise power, W i WO uf , the expected value of the output crosstalk power, WiGRG'W, and the expected value of the desired channel signal power, (W;GJ2(S:), where G, is the dth column of G. The same values can be obtained for the uncancelled case by replacing WO with e,. The important ratios of signal-to-noise (SNR), signal-to-crosstalk (SCR), and signal-to-crosstalk-plusnoise (SCNR) are created by taking ratios of the three quantities defined above. Fig. 3 shows the required channel spacing as a function of SCR. Channel spacing is normalised to units of HWHM i o 20 3 0 CO 50 60 70 80 90 slgnal to crosstalk ratlo d B Fig. 3 Channel separation required to achieve a given SCR level for different numbers of cancellation weights Curves are lower hounds achieved by optimum weighting, symbols are results achieved by the adaptive LMS simulation (19 total channels, Gaussian passband shape,-50 dB minimum crosstalk level) bandwidths, which should be roughly equivalent to the resolution of a grating demultiplexer. A 19 channel system is modelled with the centre channel, 10, as the desired channel. The curves represent optimal weights and the symbols are simulation results which are explained in the following Section. The curves are plotted for no cancellation, two weights, four weights, and eight weights. Note the large improvement that can be gained by just using two weights to cancel the adjacent channels. LMS simulation results: A simulation of the 19 channel system was performed. The three cases examined used two. four and eight cancellation weights. In all cases the LMS step size p, was 0.06 and the desired channel was channel IO. Several channel separations were chosen and the results are plotted with symbols in Fig. 3. LMS performance is usually within 1 dB of optimum. Conclusions : Grating-based demultiplexers make available an array of channel signals. In this Letter we marry these signals with mature adaptive filter technology. Postdetection crosstalk cancellation in dense WDM receivers offers the potential to greatly increase the capacity of WDM networks. Simulations of a 19 channel system show that the required channel spacing is reduced by-30, 45 and 60% for two, four and eight weights, respectively.

An FPGA based alarm system, available of using unlimited number of inputs was programmed and put ... more An FPGA based alarm system, available of using unlimited number of inputs was programmed and put in use, in this work. A low cost FPGA RZ Easy A 2.2 was used, with its four dip or button switches acting as inputs. As soon as one or more switches are ON (bit 1), the respective LED lights on, while at the same time, seven segment display shows the number of ON state inputs, corresponding, for example, to the opened doors of a house. Simultaneously the buzzer clock algorithm is activated leading buzzer to sound. If all switches go manually to OFF state (bit 0), then all LEDs are off, buzzer stops sounding and seven segment display shows zero, thus indicating for example, that no house entries are open. The above function resembles a finite state machine, since the output state, depends on the inputs of the system. The VHDL code of our system gives the opportunity of having no limitation on the number of inputs and also the ability of changing the ringing rate of the buzzer.

The electrical characteristics of the Al/a-SiC/c-Si(p)/c-Si(n +)/Al switches were successfully si... more The electrical characteristics of the Al/a-SiC/c-Si(p)/c-Si(n +)/Al switches were successfully simulated here for the first time. Forward breakover voltage V BF , forward voltage drop V F and anode current simulated values of the device showed very good agreement with the experimental results. Electric field and impact generation rate across the switches are also simulated for different anode current conditions extending to second breakdown region of the device, showing a shifting of the phenomena caused by electric field and impact generation rate, from c-Si(p) region to a-SiC film as anode voltage values increase from V BF up to second breakdown region of the device. A both simulation and experimental based model describing the device behavior, is also presented here. Two critical facts leading to switching transition are proved to be at first a-SiC/c-Si(p) heterojunction breakdown dominated by impact generation rate and second subsequent trap filling in the amorphous film. Al/a-SiC/c-Si(p +)/c-Si(p)/c-Si(n +)/Al switches with reduced V BF and V F values, were also fabricated and successfully simulated here, enhancing the validity of our simulation procedure and making the switches candidates for ESD protection devices, also due to their advantages of high anode current value density of 5 A/mm 2 before reaching second breakdown conditions in conjunction with cheap and easy fabrication procedure mainly due to r.f. sputtering technique used for a-SiC film fabrication.

Journal of Semiconductors, 2017

A parametric study for a series of technological and geometrical parameters affecting rise time o... more A parametric study for a series of technological and geometrical parameters affecting rise time of Al/a-SiC/c-Si (p)/c-Si (n+)/Al thyristor-like switches, is presented here for the first time, using two-dimensional simulation techniques.By varying anode current values in simulation procedure we achieved very good agreement between simulation and experimental results for the rising time characteristics of the switch.A series of factors affecting the rising time of the switches are studied here.Two factors among all others studied here, exerting most significant influence, of more than one order of magnitude on the rising time, are a-SiC and c-Si (p) region widths, validating our earlier presented model for device operation.The above widths can be easily varied on device manufacture procedure.We also successfully simulated the rising time characteristics of our earlier presented simulated improved switch, with forward breakover voltage VBF=11 V and forward voltage drop VF=9.5 V at the ON state, exhibiting an ultra low rise time value of less than 10 ps, which in conjunction with its high anode current density values of 12 A/mm2 and also cheap and easy fabrication techniques, makes this switch appropriate for ESD protection as well as RF MEMS and NEMS applications.

Journal of Vacuum Science & Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phenomena, 2017

Deep level traps detection and characterization in polycrystalline ZnO thin films have been inves... more Deep level traps detection and characterization in polycrystalline ZnO thin films have been investigated by deep level transient spectroscopy (DLTS) on Pd/ZnO Schottky contacts. Τhe influence of different amounts of incorporated hydrogen in ZnO layers on the creation and evolution of these traps has been studied as well. The films were deposited on n-Si substrates with direct current-sputtering, varying the hydrogen, H, flow rate in the Ar/H sputtering gas, so that the H per volume concentration [H2] was 0%, 20%, 33.3%, 50%, and 66.6%. The Pd/ZnO contacts are more stable and reliable for DLTS characterization than the respective Au/ZnO ones. Four deep electron traps were detected in all samples, referred to as traps A, B, C, and D, with respective activation energies of 0.30, 0.21, 0.47, and 0.54 eV. Another trap, E (0.61 eV), was found in the 50% and 66.6% H2 samples. Traps A and B, which are commonly observed in ZnO, are related to intrinsic defects. Trap C is attributed to surfac...

We presented here for the first time a parametric study for a series of technological and geometr... more We presented here for the first time a parametric study for a series of technological and geometrical parameters affecting the electrical characteristics of Al/a-SiC/c-Si(p)/c-Si(n +)/Al thyristor like switches using two dimensional simulation techniques. A series of factors affecting the electrical characteristics of the switches are studied here. Three factors, among all others studied here, exerting most significant influence on both first and second breakdown of the switches are amorphous SiC film width and both c-Si(p) region width and doping concentration. The above factors can be easily varied on device manufacture procedure and their combination, also including all other factors studied here, led to improved electrical characteristics of the switches. This means lowering of forward breakover voltage V BF at first breakdown and forward voltage drop V F after first breakdown at the ON state of the switch to 11V and 9.5V, respectively. This in conjunction with exhibited high anode current density values of 12A/mm 2 before second breakdown and also their cheap and easy fabrication techniques and their high switching speed behavior, makes the switches candidates for ESD protection applications.

Microelectronics Journal, 1998

The reversible effect of various factors, such as temperature, light intensity and potential appl... more The reversible effect of various factors, such as temperature, light intensity and potential applied to a gate electrode, on the electrical characteristics of new high-speed a-Si/c-Siand a-SiC/c-Si-based switches are, for the first time, presented and discussed in this paper. The irreversible effect of the width of amorphous film on the electrical characteristics of these switches is also studied. The values of forward breakover voltage (VBF), forward voltage drop (VF) and holding current (Ih) of these thyristor-like switches may be either reversibly or irreversibly controlled by varying the above factors, thus controlling the device operation.

Active and Passive Electronic Components, 1996

The electrical and optical characteristics of the new high-speed Al/a-Si/c-Si(p)/c-Si(n+)/Al and ... more The electrical and optical characteristics of the new high-speed Al/a-Si/c-Si(p)/c-Si(n+)/Al and Al/a- SiC/c-Si(p)/c-Si(n+)/Al optically controlled switches are presented in this paper. These switches exhibit the lowest ever reported values of rise and fall times, for this kind of switches, of about 3ns. They also exhibit a temperature and light reversibly controlled forward breakover voltage (VBF), together with high values of light triggering sensitivity.

Semiconductor Science and Technology, 1995

The fabrication and characteristics of Al/a-Sijcsi(p)/GSi(n+)/Al and Ai/aSiC/c-Si(p)/c-Si(n')/Al ... more The fabrication and characteristics of Al/a-Sijcsi(p)/GSi(n+)/Al and Ai/aSiC/c-Si(p)/c-Si(n')/Al switches are presented. Both switches use a non-hydrogenated amorphous thin film. The devices can be optically controlled, and exhibit forward breakover voltages (VeF) of 120-160 V. Their behaviour resembles that of a thyristor. A simple model for the device operation is also presented and discussed for the first time.

We present here an FPGA-based system, capable of simultaneous measuring and control of visible an... more We present here an FPGA-based system, capable of simultaneous measuring and control of visible and infrared lighting, temperature and humidity values of a greenhouse or industrial environment. The system uses DE10-Lite FPGA board with four sensors connected to it and in conjunction with the easy way of expanding both its software and hardware by adding more sensors, in order to cover larger areas, it is considered to be of low cost. All sensors and time values act as input. Sensors' range values and time duration for each of them are initially set by the programmer. The program used in this work converts analog inputs to digital values and displays corresponding voltage measurements in seven-segment displays of the board. A series of processes is activated upon system is set to ON, in order to achieve checking and control of parameter values. Blue LEDs and corresponding control systems are activated if related sensors' values become less than lower critical values set by programmer, while red LEDs and corresponding control systems are activated for sensors' values overcoming upper critical values. Especially for visible light values, step motor for opening or closing curtains is also activated and FPGA's board LEDs and buzzer connected to it are also ON, when upper critical value is exceeded. Yellow LEDs are activated for each parameter exceeding time set values. Finally an alarm level system turns on corresponding LEDs, depending on the number of parameter values that simultaneously exceed range values set by programmer.

A g-sensor based alarm system, available for use in many tilt sensor applications, was programmed... more A g-sensor based alarm system, available for use in many tilt sensor applications, was programmed and put in use in this work. The DE10-Lite FPGA was used, with its digital accelerometer sensor module ADXL345. The tilt sensor is programmed to present in seven segment display of the FPGA board, angle values from 0 to 90 degrees, using minus sign when the slope is to the right and the positive one when it tilts to the left, thus informing us about the sensor's tilt direction. Simultaneously the FPGA's right or left LEDs light up according to system tilt. It also uses key button for freezing its operation, hence presenting the latest angle value. The program controlling the sensor gives the ability of entering a critical angle value, depending on the application. As soon as this value is exceeded buzzer is activated, thus giving our system an alarm behavior.

Electronics Letters, 1992

(HWHM) channel separations. The LMS algorithm was initiated at iteration 300. SCR improved from 2... more (HWHM) channel separations. The LMS algorithm was initiated at iteration 300. SCR improved from 2.5 to 35 dB. The SCR using optimum weights from eqn. 2 is 37 dB. Before proceeding the performance criteria will be defined. The results of eqn. 2 are optimum and can be used as an upper bound for the performance of any cancellation algorithms. Given WO, three important quantities can be calculated. These are the expected value of the output noise power, W i WO uf , the expected value of the output crosstalk power, WiGRG'W, and the expected value of the desired channel signal power, (W;GJ2(S:), where G, is the dth column of G. The same values can be obtained for the uncancelled case by replacing WO with e,. The important ratios of signal-to-noise (SNR), signal-to-crosstalk (SCR), and signal-to-crosstalk-plusnoise (SCNR) are created by taking ratios of the three quantities defined above. Fig. 3 shows the required channel spacing as a function of SCR. Channel spacing is normalised to units of HWHM i o 20 3 0 CO 50 60 70 80 90 slgnal to crosstalk ratlo d B Fig. 3 Channel separation required to achieve a given SCR level for different numbers of cancellation weights Curves are lower hounds achieved by optimum weighting, symbols are results achieved by the adaptive LMS simulation (19 total channels, Gaussian passband shape,-50 dB minimum crosstalk level) bandwidths, which should be roughly equivalent to the resolution of a grating demultiplexer. A 19 channel system is modelled with the centre channel, 10, as the desired channel. The curves represent optimal weights and the symbols are simulation results which are explained in the following Section. The curves are plotted for no cancellation, two weights, four weights, and eight weights. Note the large improvement that can be gained by just using two weights to cancel the adjacent channels. LMS simulation results: A simulation of the 19 channel system was performed. The three cases examined used two. four and eight cancellation weights. In all cases the LMS step size p, was 0.06 and the desired channel was channel IO. Several channel separations were chosen and the results are plotted with symbols in Fig. 3. LMS performance is usually within 1 dB of optimum. Conclusions : Grating-based demultiplexers make available an array of channel signals. In this Letter we marry these signals with mature adaptive filter technology. Postdetection crosstalk cancellation in dense WDM receivers offers the potential to greatly increase the capacity of WDM networks. Simulations of a 19 channel system show that the required channel spacing is reduced by-30, 45 and 60% for two, four and eight weights, respectively.

An FPGA based alarm system, available of using unlimited number of inputs was programmed and put ... more An FPGA based alarm system, available of using unlimited number of inputs was programmed and put in use, in this work. A low cost FPGA RZ Easy A 2.2 was used, with its four dip or button switches acting as inputs. As soon as one or more switches are ON (bit 1), the respective LED lights on, while at the same time, seven segment display shows the number of ON state inputs, corresponding, for example, to the opened doors of a house. Simultaneously the buzzer clock algorithm is activated leading buzzer to sound. If all switches go manually to OFF state (bit 0), then all LEDs are off, buzzer stops sounding and seven segment display shows zero, thus indicating for example, that no house entries are open. The above function resembles a finite state machine, since the output state, depends on the inputs of the system. The VHDL code of our system gives the opportunity of having no limitation on the number of inputs and also the ability of changing the ringing rate of the buzzer.

The electrical characteristics of the Al/a-SiC/c-Si(p)/c-Si(n +)/Al switches were successfully si... more The electrical characteristics of the Al/a-SiC/c-Si(p)/c-Si(n +)/Al switches were successfully simulated here for the first time. Forward breakover voltage V BF , forward voltage drop V F and anode current simulated values of the device showed very good agreement with the experimental results. Electric field and impact generation rate across the switches are also simulated for different anode current conditions extending to second breakdown region of the device, showing a shifting of the phenomena caused by electric field and impact generation rate, from c-Si(p) region to a-SiC film as anode voltage values increase from V BF up to second breakdown region of the device. A both simulation and experimental based model describing the device behavior, is also presented here. Two critical facts leading to switching transition are proved to be at first a-SiC/c-Si(p) heterojunction breakdown dominated by impact generation rate and second subsequent trap filling in the amorphous film. Al/a-SiC/c-Si(p +)/c-Si(p)/c-Si(n +)/Al switches with reduced V BF and V F values, were also fabricated and successfully simulated here, enhancing the validity of our simulation procedure and making the switches candidates for ESD protection devices, also due to their advantages of high anode current value density of 5 A/mm 2 before reaching second breakdown conditions in conjunction with cheap and easy fabrication procedure mainly due to r.f. sputtering technique used for a-SiC film fabrication.

Journal of Semiconductors, 2017

A parametric study for a series of technological and geometrical parameters affecting rise time o... more A parametric study for a series of technological and geometrical parameters affecting rise time of Al/a-SiC/c-Si (p)/c-Si (n+)/Al thyristor-like switches, is presented here for the first time, using two-dimensional simulation techniques.By varying anode current values in simulation procedure we achieved very good agreement between simulation and experimental results for the rising time characteristics of the switch.A series of factors affecting the rising time of the switches are studied here.Two factors among all others studied here, exerting most significant influence, of more than one order of magnitude on the rising time, are a-SiC and c-Si (p) region widths, validating our earlier presented model for device operation.The above widths can be easily varied on device manufacture procedure.We also successfully simulated the rising time characteristics of our earlier presented simulated improved switch, with forward breakover voltage VBF=11 V and forward voltage drop VF=9.5 V at the ON state, exhibiting an ultra low rise time value of less than 10 ps, which in conjunction with its high anode current density values of 12 A/mm2 and also cheap and easy fabrication techniques, makes this switch appropriate for ESD protection as well as RF MEMS and NEMS applications.

Journal of Vacuum Science & Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phenomena, 2017

Deep level traps detection and characterization in polycrystalline ZnO thin films have been inves... more Deep level traps detection and characterization in polycrystalline ZnO thin films have been investigated by deep level transient spectroscopy (DLTS) on Pd/ZnO Schottky contacts. Τhe influence of different amounts of incorporated hydrogen in ZnO layers on the creation and evolution of these traps has been studied as well. The films were deposited on n-Si substrates with direct current-sputtering, varying the hydrogen, H, flow rate in the Ar/H sputtering gas, so that the H per volume concentration [H2] was 0%, 20%, 33.3%, 50%, and 66.6%. The Pd/ZnO contacts are more stable and reliable for DLTS characterization than the respective Au/ZnO ones. Four deep electron traps were detected in all samples, referred to as traps A, B, C, and D, with respective activation energies of 0.30, 0.21, 0.47, and 0.54 eV. Another trap, E (0.61 eV), was found in the 50% and 66.6% H2 samples. Traps A and B, which are commonly observed in ZnO, are related to intrinsic defects. Trap C is attributed to surfac...

We presented here for the first time a parametric study for a series of technological and geometr... more We presented here for the first time a parametric study for a series of technological and geometrical parameters affecting the electrical characteristics of Al/a-SiC/c-Si(p)/c-Si(n +)/Al thyristor like switches using two dimensional simulation techniques. A series of factors affecting the electrical characteristics of the switches are studied here. Three factors, among all others studied here, exerting most significant influence on both first and second breakdown of the switches are amorphous SiC film width and both c-Si(p) region width and doping concentration. The above factors can be easily varied on device manufacture procedure and their combination, also including all other factors studied here, led to improved electrical characteristics of the switches. This means lowering of forward breakover voltage V BF at first breakdown and forward voltage drop V F after first breakdown at the ON state of the switch to 11V and 9.5V, respectively. This in conjunction with exhibited high anode current density values of 12A/mm 2 before second breakdown and also their cheap and easy fabrication techniques and their high switching speed behavior, makes the switches candidates for ESD protection applications.

Microelectronics Journal, 1998

The reversible effect of various factors, such as temperature, light intensity and potential appl... more The reversible effect of various factors, such as temperature, light intensity and potential applied to a gate electrode, on the electrical characteristics of new high-speed a-Si/c-Siand a-SiC/c-Si-based switches are, for the first time, presented and discussed in this paper. The irreversible effect of the width of amorphous film on the electrical characteristics of these switches is also studied. The values of forward breakover voltage (VBF), forward voltage drop (VF) and holding current (Ih) of these thyristor-like switches may be either reversibly or irreversibly controlled by varying the above factors, thus controlling the device operation.

Active and Passive Electronic Components, 1996

The electrical and optical characteristics of the new high-speed Al/a-Si/c-Si(p)/c-Si(n+)/Al and ... more The electrical and optical characteristics of the new high-speed Al/a-Si/c-Si(p)/c-Si(n+)/Al and Al/a- SiC/c-Si(p)/c-Si(n+)/Al optically controlled switches are presented in this paper. These switches exhibit the lowest ever reported values of rise and fall times, for this kind of switches, of about 3ns. They also exhibit a temperature and light reversibly controlled forward breakover voltage (VBF), together with high values of light triggering sensitivity.

Semiconductor Science and Technology, 1995

The fabrication and characteristics of Al/a-Sijcsi(p)/GSi(n+)/Al and Ai/aSiC/c-Si(p)/c-Si(n')/Al ... more The fabrication and characteristics of Al/a-Sijcsi(p)/GSi(n+)/Al and Ai/aSiC/c-Si(p)/c-Si(n')/Al switches are presented. Both switches use a non-hydrogenated amorphous thin film. The devices can be optically controlled, and exhibit forward breakover voltages (VeF) of 120-160 V. Their behaviour resembles that of a thyristor. A simple model for the device operation is also presented and discussed for the first time.