Fred W. Schmidlin

Enhanced Tunneling through Dielectric Films due to Ionic Defects

The theoretical shape of the potential barrier for a dielectric film interposed between two metals is discussed, with particular emphasis on the effects arising from ionic defects, interfacial dipoles, and field penetration of the electrodes. It is shown that both ions and the extension of their electric fields penetrating the electrodes have a significant effect on barrier shape. By applying Strattons theory of tunneling, an analytic expression is obtained for the increase of tunnel current due to ion penetration of the barrier. For ion concentrations of the order of one per unit area equal to the film thickness square, the tunnel current increases by an order of magnitude. Numerical results are also presented for an Al–Al2O3–Al barrier, where the analytic solution is only marginally valid.

Theory of multiple trapping

Abstract An analytic solution of the conventional multiple trapping problem is presented for the complete time domain and an arbitrary distribution of traps. The solution reduces to previously published solutions in appropriate limits. New methods are proposed for determining the microscopic mobility and trap densities.

A new nonlevitated mode of traveling wave toner transport

A mode of transporting charged particles with a traveling electrostatic wave is described. Structures specifically designed to produce a running wave of sufficient strength to move a typical xerographic toner along a surface without altering their charge are described. Experimental results are presented which show that the toner particles move synchronously with the wave as tiny clouds. Thus the transport mode is akin to the hopping mode yet distinguishable from it because the present mode is not functional in the low-frequency region studied. Measurements of the mass transport rate that characterize the present mode of transport are presented, along with representative development characteristics which illustrate the potential of traveling-wave transport as a sensitive scavengeless xerographic development process.<<ETX>>

Charge Transport and Photoconductivity in Amorphous Arsenic Trisulfide Films

Charge transport and photoconductivity in As2S3 amorphous films have been investigated at a temperature of 25°C. It is found that holes are the mobile carriers in As2S3 whereas electrons are quite immobile in the material. The photoconductivity is mainly governed by the product of the photogeneration efficiency and the schubweg of the generated holes. Both of these quantities are electric field dependent. Carrier transport is essentially dominated by bulk trapping. The traps are distributed in energies above the hole conduction states. The release rate of the trapped charges varies since the rate is an inverse function of the trap energy. A theoretical model describing the transport process is presented to account for the experimental results. The photogeneration efficiency as a function of electric field at high fields (greater than 105 V/cm) has been determined for incident photon energies of 2.5–3.1 eV. The generation efficiency is observed to decrease in the same manner as the absorption coefficient w...

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.

Transient photostimulated charge transfer from a photoconductor to an insulating fluid

An investigation was made of photostimulated transfer of charge from a photoconductor into an insulating fluid. A theoretical description of the dynamics of charge−carrier generation and transport in the photoconductor, carrier accumulation at the photoconductor−fluid interface, and charge exchange into the fluid was developed in which the various physical processes are characterized by rate constants. Measurements of the dependence on electric field, light intensity, sample thickness, and carrier mobility in the fluid were carried out to determine which current−limiting mechanisms are dominant. The results illustrate a method of separately determining the interfacial charge−transfer efficiency and the efficiency of supplying photogenerated carriers to the interface.

Physical theory of charged pigment electrophotography

A formal approach to the theory of electrophotography is introduced in which imaging systems are defined and classified according to the dominant physical interactions responsible for the imaging process. The usefulness of the approach lies in the fact that it provides a powerful means of comparative analysis as well as ideal standards against which the performance of real systems can be compared. Application of the theory to charged pigment electro-photography, defined as that branch of electrophotography which exploits the electric field-monopole interaction to drive development, naturally leads to two broad subclasses: charged pigment xerography (CPX), in which development is achieved through the interaction of uniformly charged pigment with a varying electric field; and photoactive pigment electrophotography (PAPE), in which development is achieved through the interaction of a uniform electric field with a varying charge on the pigment. A comparative study of the two systems reveals that the inherent noisiness of adhesion severely limits their sensitivity when it must be coped with directly. Under these circumstances, it is further seen that fluctuations in charge on the pigment leads (via the electrostatic image force) to a limitation of the force available for driving development in CPX only. Since the same limitation does not arise in PAPE, any system of the latter type may have a sensitivity two orders of magnitude higher than its corresponding CPX system, providing the two are equivalent in every other respect (equal resolving power and latent image forming efficiency).