Otto configuration attenuated total reflection (ATR) measurements of the excitation of surface pl... more Otto configuration attenuated total reflection (ATR) measurements of the excitation of surface plasmons in the infrared have been carried out on YBCO films deposited on MgO (100) substrates. The dielectric constants for YBCO at 3.392μm are determined to be −10+15i forc-axis material. The anisotropic nature of the cuprate is seen from films with other orientations: nearlya-axis material has constants of 4.0+7.0i. It is thus not metallic in its optical response along thec-axis which lies parallel to the substrate plane. Ellipsometric measurements in the visible onc-axis material point to a maximum surface plasmon energy of 1 eV.
Monte Carlo calculations of quantum yield in PtSi/p-Si infrared detectors are carried out taking ... more Monte Carlo calculations of quantum yield in PtSi/p-Si infrared detectors are carried out taking into account the presence of a spatially distributed barrier potential. In the 1-4 0268-1242/13/7/007/img5m wavelength range it is found that the spatial inhomogeneity of the barrier has no significant effect on the overall device photoresponse. However, above 0268-1242/13/7/007/img6m and particularly as the cut-off wavelength (0268-1242/13/7/007/img7m) is approached, these calculations reveal a difference between the homogeneous and inhomogeneous barrier photoresponse which becomes increasingly significant and exceeds 50% at 0268-1242/13/7/007/img8m. It is, in fact, the inhomogeneous barrier which displays an increased photoyield, a feature that is confirmed by approximate analytical calculations assuming a symmetric Gaussian spatial distribution of the barrier. Furthermore, the importance of the silicide layer thickness in optimizing device efficiency is underlined as a trade-off between maximizing light absorption in the silicide layer and optimizing the internal yield. The results presented here address important features which determine the photoyield of PtSi/Si Schottky diodes at energies below the Si absorption edge and just above the Schottky barrier height in particular.
Surface plasmons polaritons (SPPs) may be supported on the surface of PtSi electrodes in PtSi/Si ... more Surface plasmons polaritons (SPPs) may be supported on the surface of PtSi electrodes in PtSi/Si Schottky barrier diodes. Using a prism-air gap-PtSi/p-Si or Otto coupling configuration we have excited SPPs at temperatures below 120 K on these devices. Changes in the dip in reflectance associated with SP excitation indicates changes in the PtSi optical data as a function of temperature. However it is important to understand what the optical data describe. In general they incorporate a surface roughness layer and are not truly characteristic of the material (PtSi) itself. In this context AFM analysis of the surface topography is presented. In addition the compositional structure of the PtSi as determined from Rutherford Backscattering Spectroscopy is discussed.
Excitation of surface plasmons by attenuated total reflection is used to optically characterize p... more Excitation of surface plasmons by attenuated total reflection is used to optically characterize platinum silicide films and to produce enhanced photosignals from PtSi-Si Schottky barrier devices. In this work the Otto configuration (prism-air gap-sample) for attenuated total reflection is used to excite the mode at the air-PtSi interface on PtSi-Si structures; surface plasmon excitation is evidenced as a prominent dip in measurement of reflectance as a function of internal angle of incidence in the prism. Coupling efficiencies of 90 - 95% between incoming p-polarized radiation and surface plasmons on PtSi have been achieved at wavelengths ranging from the visible to the infrared (0.633 micrometers to 3.39 micrometers ). The surface plasmon energy is dissipated by absorption through the creation of electron-hole pairs in the lossy silicide layer. Subsequent hot carrier emission over the Schottky barrier can thus yield an enhanced photosignal associated with the enhanced absorption due to surface plasmon excitation--initial results demonstrating this phenomenon are reported. here. Finally, reflectivity calculations show also the possibility of infrared surface plasmon excitation in PtSi grating structures with periodicity of the same order as the wavelength.
ABSTRACT It is shown that surface plasmons (SPs) are supported on thin PtSi films. Using a prism-... more ABSTRACT It is shown that surface plasmons (SPs) are supported on thin PtSi films. Using a prism-air gap-sample configuration, p-polarised infra-red light (3.39 mu m) has been coupled with approximately 95% efficiency to SPs on the silicide electrode of PtSi-Si Schottky barrier structures, stimulating SPs offers both a means of optically characterising silicide films and of enhancing optical absorption with a view to significantly increasing the Schottky barrier photoresponse.
Surface plasmons have been observed directly in YBCO films in an Otto-geometry attenuated total r... more Surface plasmons have been observed directly in YBCO films in an Otto-geometry attenuated total reflection measurement at a wavelength of 3.392 mum. The laser deposited films are c-axis oriented on an MgO substrate. This observation confirms theoretical deductions from complex dielectric function data. Measured data have been fitted to a theoretical model and are compared with the optical constants determined
Current-voltage (I-V) and capacitance-voltage (C-V) characteristics of He-ion irradiated Pd/n-Si0... more Current-voltage (I-V) and capacitance-voltage (C-V) characteristics of He-ion irradiated Pd/n-Si09Ge0.10 Schottky contacts have been measured in the temperature range from 100 to 300 K. Schottky barrier properties such as the Schottky barrier height (Phibn) and ideality factor (n) have been studied as a function of temperature. The degree to which their characteristics deviated from the ideal case increased as the
ABSTRACT Pd/Si0.9Ge0.1/Si Schottky barrier diodes subjected to irradiation are characterized usin... more ABSTRACT Pd/Si0.9Ge0.1/Si Schottky barrier diodes subjected to irradiation are characterized using capacitance and conductance measurements performed under forward and reverse bias while varying the temperature and frequency. The C–V technique has been used in particular to determine the carriers profile as well as the interface state density and its energy distribution.
ABSTRACT Using the analogue behavioural modelling capabilities of Pspice, the current– voltage ch... more ABSTRACT Using the analogue behavioural modelling capabilities of Pspice, the current– voltage characteristics and the large-signal equivalent circuit of a resonant tunneling diode are exploited to create a Pspice compatible model for the diode. The model is used, with very few other components, in the simulation of a number of circuit applications, including a sinusoidal wave generator, a frequency multiplier and three state logic circuits. The simulated circuit details, the related waveforms and three-state logic operations are described. The circuits are characterized mainly by their reduced complexity and ease of analysis.
The small signal impedance of GaAs/Al(Ga)As double-barrier resonant tunnel diodes has been measur... more The small signal impedance of GaAs/Al(Ga)As double-barrier resonant tunnel diodes has been measured and analyzed over a wide range of frequencies and for various d.c. bias values. The RTD equivalent circuit elements were obtained by measuring the impedance in the bistable region. The cut-off frequency and the self-resonant frequency were calculated and compared with direct measurements.
Otto configuration attenuated total reflection (ATR) measurements of the excitation of surface pl... more Otto configuration attenuated total reflection (ATR) measurements of the excitation of surface plasmons in the infrared have been carried out on YBCO films deposited on MgO (100) substrates. The dielectric constants for YBCO at 3.392μm are determined to be −10+15i forc-axis material. The anisotropic nature of the cuprate is seen from films with other orientations: nearlya-axis material has constants of 4.0+7.0i. It is thus not metallic in its optical response along thec-axis which lies parallel to the substrate plane. Ellipsometric measurements in the visible onc-axis material point to a maximum surface plasmon energy of 1 eV.
Monte Carlo calculations of quantum yield in PtSi/p-Si infrared detectors are carried out taking ... more Monte Carlo calculations of quantum yield in PtSi/p-Si infrared detectors are carried out taking into account the presence of a spatially distributed barrier potential. In the 1-4 0268-1242/13/7/007/img5m wavelength range it is found that the spatial inhomogeneity of the barrier has no significant effect on the overall device photoresponse. However, above 0268-1242/13/7/007/img6m and particularly as the cut-off wavelength (0268-1242/13/7/007/img7m) is approached, these calculations reveal a difference between the homogeneous and inhomogeneous barrier photoresponse which becomes increasingly significant and exceeds 50% at 0268-1242/13/7/007/img8m. It is, in fact, the inhomogeneous barrier which displays an increased photoyield, a feature that is confirmed by approximate analytical calculations assuming a symmetric Gaussian spatial distribution of the barrier. Furthermore, the importance of the silicide layer thickness in optimizing device efficiency is underlined as a trade-off between maximizing light absorption in the silicide layer and optimizing the internal yield. The results presented here address important features which determine the photoyield of PtSi/Si Schottky diodes at energies below the Si absorption edge and just above the Schottky barrier height in particular.
Surface plasmons polaritons (SPPs) may be supported on the surface of PtSi electrodes in PtSi/Si ... more Surface plasmons polaritons (SPPs) may be supported on the surface of PtSi electrodes in PtSi/Si Schottky barrier diodes. Using a prism-air gap-PtSi/p-Si or Otto coupling configuration we have excited SPPs at temperatures below 120 K on these devices. Changes in the dip in reflectance associated with SP excitation indicates changes in the PtSi optical data as a function of temperature. However it is important to understand what the optical data describe. In general they incorporate a surface roughness layer and are not truly characteristic of the material (PtSi) itself. In this context AFM analysis of the surface topography is presented. In addition the compositional structure of the PtSi as determined from Rutherford Backscattering Spectroscopy is discussed.
Excitation of surface plasmons by attenuated total reflection is used to optically characterize p... more Excitation of surface plasmons by attenuated total reflection is used to optically characterize platinum silicide films and to produce enhanced photosignals from PtSi-Si Schottky barrier devices. In this work the Otto configuration (prism-air gap-sample) for attenuated total reflection is used to excite the mode at the air-PtSi interface on PtSi-Si structures; surface plasmon excitation is evidenced as a prominent dip in measurement of reflectance as a function of internal angle of incidence in the prism. Coupling efficiencies of 90 - 95% between incoming p-polarized radiation and surface plasmons on PtSi have been achieved at wavelengths ranging from the visible to the infrared (0.633 micrometers to 3.39 micrometers ). The surface plasmon energy is dissipated by absorption through the creation of electron-hole pairs in the lossy silicide layer. Subsequent hot carrier emission over the Schottky barrier can thus yield an enhanced photosignal associated with the enhanced absorption due to surface plasmon excitation--initial results demonstrating this phenomenon are reported. here. Finally, reflectivity calculations show also the possibility of infrared surface plasmon excitation in PtSi grating structures with periodicity of the same order as the wavelength.
ABSTRACT It is shown that surface plasmons (SPs) are supported on thin PtSi films. Using a prism-... more ABSTRACT It is shown that surface plasmons (SPs) are supported on thin PtSi films. Using a prism-air gap-sample configuration, p-polarised infra-red light (3.39 mu m) has been coupled with approximately 95% efficiency to SPs on the silicide electrode of PtSi-Si Schottky barrier structures, stimulating SPs offers both a means of optically characterising silicide films and of enhancing optical absorption with a view to significantly increasing the Schottky barrier photoresponse.
Surface plasmons have been observed directly in YBCO films in an Otto-geometry attenuated total r... more Surface plasmons have been observed directly in YBCO films in an Otto-geometry attenuated total reflection measurement at a wavelength of 3.392 mum. The laser deposited films are c-axis oriented on an MgO substrate. This observation confirms theoretical deductions from complex dielectric function data. Measured data have been fitted to a theoretical model and are compared with the optical constants determined
Current-voltage (I-V) and capacitance-voltage (C-V) characteristics of He-ion irradiated Pd/n-Si0... more Current-voltage (I-V) and capacitance-voltage (C-V) characteristics of He-ion irradiated Pd/n-Si09Ge0.10 Schottky contacts have been measured in the temperature range from 100 to 300 K. Schottky barrier properties such as the Schottky barrier height (Phibn) and ideality factor (n) have been studied as a function of temperature. The degree to which their characteristics deviated from the ideal case increased as the
ABSTRACT Pd/Si0.9Ge0.1/Si Schottky barrier diodes subjected to irradiation are characterized usin... more ABSTRACT Pd/Si0.9Ge0.1/Si Schottky barrier diodes subjected to irradiation are characterized using capacitance and conductance measurements performed under forward and reverse bias while varying the temperature and frequency. The C–V technique has been used in particular to determine the carriers profile as well as the interface state density and its energy distribution.
ABSTRACT Using the analogue behavioural modelling capabilities of Pspice, the current– voltage ch... more ABSTRACT Using the analogue behavioural modelling capabilities of Pspice, the current– voltage characteristics and the large-signal equivalent circuit of a resonant tunneling diode are exploited to create a Pspice compatible model for the diode. The model is used, with very few other components, in the simulation of a number of circuit applications, including a sinusoidal wave generator, a frequency multiplier and three state logic circuits. The simulated circuit details, the related waveforms and three-state logic operations are described. The circuits are characterized mainly by their reduced complexity and ease of analysis.
The small signal impedance of GaAs/Al(Ga)As double-barrier resonant tunnel diodes has been measur... more The small signal impedance of GaAs/Al(Ga)As double-barrier resonant tunnel diodes has been measured and analyzed over a wide range of frequencies and for various d.c. bias values. The RTD equivalent circuit elements were obtained by measuring the impedance in the bistable region. The cut-off frequency and the self-resonant frequency were calculated and compared with direct measurements.
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