The field and light induced emission of electrons from ITO film into vacuum has been investigated. Under influence of applied voltage, within the interval from -2 kV to 0V, electron emission into vacuum occured. With increasing voltage and under illumination the electron emission grows monotonically. At low voltage (≤ |-500V|) the increase is linear. At higher voltage this dependence is exponential. Upon the internal field and illumination influence, the emission is about
twice as much as without illumination. This may be evidence that the electric field initiates electron collisions, which proceed according to the impact ionization mechanism. The emission intensity-electron energy distribution was found to be close to the Gauss probability function. We have also found the Poisson distribution can be used instead of the Gauss one.
A probabilistic approach has been used to analyze the stability of the various finite difference formulations for propagation of signals on a lossy transmission line. We extend the concept to consider the effects of space and time discretisations on the signs of the coefficients in a probabilistic finite difference implementation of the Telegraphers’ equation. We have found that if the sign of certain transition probabilities is negative then the algorithm is found to be unstable. The results of numerical analysis show that the following formulations of the diffusion and the Telegrapher’s equation gives the acceptable solutions: the backward difference, the central difference and Telegraphers’ equation with combination of central and backward differences. However the forward difference formulation of the diffusion equation gives the different results.
The work contains results of investigation on the phenomena of the field induced electron emission in thin oxide layers. As the emitters were used the thin doped films of In2O3 and SnO2 (ITO-indium tin oxide) of thickness 10-300 nm deposited on 0.2 mm thick sodium glass plate. A negative voltage Upol was applied to the sample’s field electrode. The ITO film was subjected to the bombardment by primary electron beam of energy Ep, which equals 200 eV. The field induced the secondary emission effect was studied in the 10-7 hPa vacuum. The dependence of the secondary emission coefficient δ on the electric field was found to be not monotonic. The dependence δ= f(Ep) was also found to be different from that typically described in the literature. Energy examination of the emitted electrons revealed some electrons of energy higher than Ep. After removing the primary electron beam the electron emission still existed due to the applied electric field and it is called the electric field induced electron emission (EFIEE). The emission currents were of the order of nA. About 80% of the emitted electrons were found of energy within 1-2 eV, however few percent of the electrons exhibited energy approaching 10 eV. With increasing the applied voltage the emitted electron flux increased. It concerns mainly the low-energy electrons. The energy distribution of the electrons emitted under the EFIEE conditions from SI-SiO2-ITO structures was also studied. The phenomenological model was proposed of the EFIEE effects. The main assumptions of the model are supported on the basis of the field induced division of the ITO semiconductor into two zones: depleted and enhanced of electrons.
Electron emission properties of doped In203 and Sn02 (ITO) thin layers have been studied. These layers have been deposited onto both surfaces of a microscope glass using a constant-current ion sputtering method. One of the layer
(1 μm thick) was a field electrode and another one (1Onm - 200nm) was treated as an electron emitter. The layers were examined using an electron emission induced by electric field. The polarizing voltage Upol has been applied to the field electrode. The studies has been carried out in vacuum (1O-7 hPa). Electron emission yield dependence on the intensity of an internal field and illumination were measured. The exponential dependence of the pulse frequency n =f(Upol) has been found. With increasing Upol (field strength in a sample) and after illumination the count frequency of pulses grows monotonically. At low Upol (≤|-500V|) the increase is linear. At higher Upol this dependence is exponential. Energy analysis of emitted electrons was performed by the retarding field method. Measurements of electrons energy in field induced emission showed that about 80% of electrons have energy up to 10 eV. It was also found that additional effect at simultaneous emission oftwo electrons as result ofabsorption of a single photon have to be taken into account.
The thin transparent and conductive ITO layers have been deposited onto the both surface of the glass of dimensions 0.2 X 16 X 16 mm using the DC ion sputtering method. In order to study the electron emission the voltage has been applied between the both ITO layers. One of the layer was 1 micrometer thick (field electrode) and another one (10 divided by 200 nm) at opposites surface of the glass surface was treated as the electron emitter. The negative biasing voltage has been applied to the field electrode. The studies has been carried out in vacuum (10-7 hPa). The multichannel analyzer of amplitude of voltage pulses created by the electron multiplier has been used in order to record the electron emission yield. The pulses are recorded in channels of the pulse analyzer according to their height creating so-called voltage pulse amplitude spectrum. Aside of the effects the studies concerning the result of UV illumination on the photoemission monitored by field has been examined. With increasing of biasing voltage (0 divided by -2 kV) and after illumination the count frequency of pulses grows monotonically. The shape of obtained curves of the spectral dependence of the photoelectron emission yield was found to be independent of the excitation wavelength. However, the surface under the experimental curves were found to be different and the maximal one appeared to be for the wavelength corresponding approximately for the value of the energy gap of ITO (3.5 eV).
Using the controlled Malter effect the study was carried out on the application of ITO type oxide layers (In2O3-Sn, SnO2-Sb, 10 nm and 200 nm) deposited onto a glass substrate as a relatively stable electron emitter. The polarizing voltage Upol has been applied to the field electrode. The investigations were performed in the vacuum of the order 10-6Pa. As a result of applying Upol and illumination, electrons and photoelectrons are released and enter electron multiplier. The electrons create voltage pulses in the multiplier which are recorded in the multichannel pulse amplitude analyzer. The amplitude spectra N(U) equals f(U) were measured for unilluminated samples and illuminated by a quartz lamp. The exponential dependence of the pulse frequency n equals f(Upol) has been found. It was also found that additional effect at simultaneous emission of two electrons (DPE - double photoelectron emission) as result of absorption of a single photon have to be taken into account. Using the retarding field method was evaluated that the emitted electron energy (in dark and under illumination) can achieve even 50 eV, but most of the electrons (about 80%) have energies from hear zero up to 10 eV. Photoinduced optical phenomena in glass-ITO system are studied using experimental spectroscopic and theoretical quantum chemical methods. Photoinduced optical second harmonic (SHG) has been also observed in these films. Theoretical calculations have shown that SnO4 tetrahedral interacting with SiO4 clusters of the glass substrate play central role in observed nonlinear photoinduced changes.
The thin transparent and conductive Sn doped In2O3 layers have been deposited onto both surfaces of the glass plate of dimensions 0.2x16x16 mm using the constant-current ion sputtering method. In order to study the electron emission the voltage has been applied between both the ITO layers. One of the layers was 1 micrometers thick (the field electrode) and another one (10nm and much thinner) was deposited onto the opposite surface of the glass. This thin layer was treated as the electron emitter. The polarizing voltage Upol has been applied to the field electrode. The study has been carried out in vacuum (10MIN7hPa). The multichannel analyzer of amplitude of voltage pulses created by the electron multiplier has been used in order to record the electron emission yield. Aside of the field effects the studies concerning the result of UV illumination on the photo emission monitored by field has been examined. Determined were the amplitude spectrum of the voltage pulses for various polarizing voltage. The same method was used to find the dependence of the pulse frequency n on the applied voltage Upol. The exponential dependence n = f(Upol) has been found. The field induced emission mechanism can be explained on the basis of the well known phenomena occurring in semiconductors under influence of strong electric field (the hot electron effect, the impact ionization, the Gunn effect, the tunnel effect, etc.). It was also found that additional effect at simultaneous emission of two electrons as a result of absorption of a single photon have to be taken into account. The existence of this effect has been proved by decomposition of the amplitude spectrum into Gaussians. Measurements of electron energy in the field induced emission showed that about 80% of electrons have energy up to 10 eV. Photo induced optical second harmonic (SHG) has been also observed in these films.
The work contains results of investigations on the phenomena of the electron emission in thin oxide layers (ITO) in which internal electric field has been generated. Two conducting and transparent films of In2O3:Sn were evaporated on both sides of a microscopic cover glass. One film of the thickness 10 divided by 20nm was the emitting surface. The other, of thickness 1 micrometers , was polarized in order to create an internal field. Applying a negative voltage Upol to field electrode created the internal electric field. The investigations were performed in the vacuum of the order 10-6Pa. As a result of applying Upol and illumination, electrons are released and enter electron multiplier. The electrons create voltage pulses in the multiplier, which are recorded in the multichannel pulse amplitude analyzer. The pulses are recorded in channels of the pulse analyzer, creating so-called voltage pulse amplitude spectrum. The amplitude spectra were measured for unilluminated samples and illuminated by a quartz lamp. With increasing Upol and after illumination the count frequency of pulses grows monotonically. At low Upol the increase is linear. At higher Upol this dependence is exponential. This may be evidence that the electric field initiates electron collisions, which proceed according to impact ionization mechanism. Photoinduced optical second harmonic has been also observed in these films. Theoretical calculations have shown that SnO4 tetrehedral interacting with SiO4 clusters of the glass substrate play central role in observed nonlinear photoinduced changes.
The work contains results of investigation on the phenomena of the electron emission and photoemission in thin oxide layers in which internal electric field has been generated. Study on secondary electron emission from complex many- layered emitters has led to the discovery of Malter's effect. Basing on it, the sample was a glass with semiconducting films evaporated on its both sides. The internal electric field was created by applying a negative voltage Upol to the field electrode. The investigations were performed in the vacuum of the order 10-6 Pa. As a result of applying Upol and illumination, electrons and photoelectrons are released and recorded as voltage pulses in the multichannel pulse amplitude analyzer. The amplitude spectra N(U) equals f(U) for various Upol were measured for not illuminated samples and illuminated ones. Electron emission yield dependence on the intensity of an internal field and illumination was measured. With increasing Upol the count frequency of pulses grows monotonically. The electric field initiates electron collisions which proceed according to the impact ionization mechanism. Energy analysis of emitted electrons was performed by the retarding field method. Measurements of electron energy in field induced emission showed that about 80 percent of electrons have energy up to 10 eV.
Influence of an inner electric field on such emission phenomena like: secondary emission, photoemission and field emission has been investigated. The applied sample-emitter was a glass wafer (thickness 0.2 mm) covered on both sides by semiconducting films In2O3:Sn. A voltage (in the interval -2000V divided by 0V) generating transverse electric field was applied to one of the films. This film had a thickness of about 200 nm. The second film (emitting electrons) had a thickness 100 nm or 10 nm. The secondary emission measurements were made by the retarding field method using four grid retarding potential analyzer. It was found that the secondary emission coefficient changes non- monotonically with increasing field intensity. Electron emission measurements without using a primary electron beam were made with the electron multiplier cooperating with a multichannel pulse amplitude analyzer. The measurements were performed in the vacuum of about 2 multiplied by 10-6 Pa. Influence of film thickness on the intensity of field controlled emission and field controlled photoemission was also studied. It was also found that the frequency of counts (generated by electrons in the electron multiplier) depends on the polarizing voltage approximately in an exponential way. Some departures from this dependence can be observed at higher Upol voltages (above 1000 V). Thus, at an appropriate high voltage Upol conditions for a cascade emission are created. At lower voltages the conditions correspond to a semiconductor with a negative electron affinity.
This work is concerned with electron emission induced by an electric field and photoemission assisted by the field. The applied samples were emitters in the shape of semiconducting films evaporated on both sides of a glass substrate of thickness 0,2 mm. One side was an emitting surface whereas the other was a field electrode. The field electrode was supplied by negative polarizing voltage Upol. The emitting materials were In2O3:Sn and titanium films. As a result of applying Upol and illumination, electrons and photoelectrons are released and enter electron multiplier. Amplitude spectra of pulses were recorded by a multichannel analyser of pulse voltage. Energy analysis of electrons released from the samples was performed by the method of retarding field. Amplitude spectra at a given Upol and changing retarding field for titanium and oxide layers were compared. It was found that electron energy can exceed even 50eV. For both types of films the influence of illumination of electron emission induced by an electric field was also investigated.
The work contains results of irivestigatior on photoemission in thin oxide layers in WhiCh internal electric field has been generated. The samples were microscopic glasses covered on both sides by coructirç layers . The internal electric field was created by applyirg a negative polarizing voltage Upot to one of the layers (field emission electrode) , whereas the other one was emitting layer (Sr :Sb, Ti ) . As a result of Upoi. voltage ard i1 lumination, electron were released from the sample . mplite distrib.itior of imp.tlses were measuremed by ampi itie multicharinel analyser (fcr ani1 hinated ard I 1lumirited samples) . For i1 luminated emitting fi ln of Sr :Sb, the frequency of cc*.inth was several times greater then for uni1 luminated samples . For titanium fi las the interity of electron emission was several ord€r of magnitte sml ler than for Sr : Sb. For al1 samples the electron emission increases with growing Upo)..
Keywords : photoemission. emission yield, semicorductor, SIS system, electric field. thin oxide layers, work function, optical properties.
This work contains results of investigations on photoemission in thin oxide layers in which internal electric field has been generated. In other works, secondary electrons of energy greater than that of primary electrons have been detected. This anomalous phenomenon is also expected in the case of photoemission controlled by the internal electric field. The investigated samples were microscopic glasses covered with conducting layers (SnO2:Sb). On one side photoemission was measured, whereas on the other side the polarizing voltage Upol which generated the electric field in the investigated layer was applied. Amplitude distributions of impulses for samples of various thickness and at various Upol were determined. The measurements were performed with a multichannel impulse amplitude analyzer (NTA 1024). For samples of thin emitting layers (about 10 nm) the amplitude spectra could be described with a Gaussian curve. For thicker samples (above 150 nm) and at sufficiently large negative voltage Upol, the spectra could be described with a sum of at least two Gaussian curves. This would be evidence of receiving two or more photoelectrons from a single light quantum.
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