Andras I. Lakatos

Transient Internal Photoemission of Carriers in the Metal‐Insulator System

The transient photoemission of hot carriers from metals into insulators permits a detailed study of the dynamics of the metal‐insulator interface. The technique can be viewed as the simulation of a transient thermionic experiment. The photoemission of electrons from copper into single‐crystal CdS and holes from gold into amorphous selenium is reported. The results are consistent with a model of backscattering out of the insulator due to interaction with the lattice. Significant differences are found between photoemission into the single crystal and amorphous insulator which could arise from the different charge transport properties of these materials, as for example dictated by their structures.

Steady−state dark and photocurrents in a poly−n−vinylcarbazole−trinitrofluorenone photoconductor

Dark and photocurrents were measured under steady−state conditions in a 1 : 0.6 molar poly−n−vinylcarbazole−trinitrofluorenone photoconductive polymer. Electric field and sample thickness measurements indicate that the dark currents are not space−charge limited but rather conform to a Poole−Frenkel or similar type field dependence at E?105 V/cm. The photocurrents generated by bulk absorbed light show linear behavior below 105 V/cm, above this field these currents increase approximately as E2. These currents are sublinear in light intensity. A model which includes the field−dependent photogeneration rate, a wide distribution of localized states in the energy gap, and field−independent free−carrier mobility is proposed to explain these results. The field dependence of surface generated hole currents shows a transition from space−charge to emission limitation with increasing applied field. Above 5×104 V/cm the field dependence of the photogeneration rate approaches an E1.5 dependence.

Photoelectric induced elastomer deformation in PVK‐TNF type γ‐RUTICON

In the γ‐RUTICON images are created with a spatially sinusoidal deformation of a metallized elastomer which is deposited on top of a photoconductor. The deformation in the elastomer is controlled by the imagewise discharge of the photoconductor when a dc bias is applied between the top metal coating and the bottom transparent electrode. This dynamic process is described in terms of a double‐layer linear dielectric model. This model is strictly applicable only in the case where the photoconductivity σp is independent of the applied field. Such is the case in the steady state for PVK‐TNF (poly‐n‐vinylcarbazole‐trinitroflourenone) at applied fields ≤2 × 105 V/cm. The model predicts the response time τ of the elastomer to be dependent only upon σp and the dielectric constants ep and ee of the photoconductor and elastomer, respectively. The maximum deformation Dmax at a given applied bias V is a function of the mechanical properties of the metallized elastomer alone. If these parameters are field independent, ...

Electric field line bending limited elastomer deformation in an a‐Se type deformographic light valve

The time development of elastomer deformation under the influence of exposure to light in the a‐Se‐type RUTICON has been characterized as a function of applied bias and light intensity. The deformation was observed to initially increase linearly while the transverse currents decrease linearly as a function of exposure time. The deformation reaches a maximum Dm at time tm, which is always ?1/2tr, the photoelectric response time for the devices tested. Also, Dm∝V2 and tm∝tr∝F−1, the latter proportionality ensures exposure intensity versus time reciprocity for the device. These features are analyzed using the characteristic photoelectric properties of a‐Se, first in terms of a simple parallel field lines model which is successful in explaining all the observed characteristics with the exception of the difference between tm and tr. The second revised model takes into account the bending of the field lines in the photoconductor during exposure to light, and it successfully describes the observed relationship b...

Double Schottky‐Barrier Capacitance on Trigonal Selenium

The low‐frequency parallel capacitance and resistance of back‐to‐back metal‐semiconductor Schottky barriers with a series bulk semiconductor resistance Rs≠0 between them has been measured on trigonal Se with In electrodes. Differential capacitance vs bias‐voltage measurements show a sharp minimum close to V = 0, similar to that observed for Ge–Si (n‐n) isotype heterojunctions. [C. van Opdorp and H. K. J. Kanerva, Solid‐State Electron. 10, 401 (1967).] This minimum is due to the relative voltage dependence of the two Schottky barriers. Ionized acceptor concentrations of 1.8–7.5×1015 cm−3 and a low‐frequency bulk conductivity of trigonal Se of 1.6×10−6 Ω−1 cm−1 are obtained from an equivalent circuit analysis.