Study of solar cell fabrication using an electrostatic thick-filmprinting method

A novel thick-film circuit printing technique which is based on the electrostatic principle known as noncontact electrostatic thick-film printing was developed for the metallization of edge-defined film-fed growth (EFG) solar cells. The conventional thick-film solar cell inks were modified by adding 10-20% terpineol solvent. The effects of ink viscosity, applied voltages, nozzle diameter, and nozzle-to-substrate distance on line definition and ink-flow rate were investigated. A simple theoretical model was derived for the electrostatic ink ejection. The minimum line width obtained was 3 mm. Multilayer printing was able to be used to raise the line film thickness. The maximum line width obtained was about 20-30 mm for a single run. The system is now completely computercontrolled and capable of printing films onto solar cell substrates reliably, with a high degree of accuracy. Multiple-layer prints can be made with food layer-to-layer registration     

Hollow-beam focusing with electrostatic and periodic magnetic fields

A new method of focusing a hollow cylindrical electron beam is presented. The focusing system consists of a cylindrical center conductor inside the beam, a cylindrical outer conductor enclosing the beam, and a series of periodic magnets outside the tube. A radial electrostatic field between the conductors provides an outward force on the electrons. The periodic magnetic field produces an inward force on the electrons. The inward and outward forces can be adjusted to provide a balance of all the forces acting on the electrons at both boundaries of the beam by choosing the electric and magnetic fields properly. An approximate analysis has been made and is presented which gives necessary design information. A number of curves are presented which are useful in designing focusing systems of this type. Experimental results on a beam tester show that current transmission of over 90 per cent for perveance up to 11 micropervs can be obtained readily. The adjustments are not critical and the performance is very stable.     

Novel method for numerical analysis of electron trajectories in electrostatic fields of implicit functional forms

A novel method for calculating 2-dimensional electron trajectories is given, which is useful for the case when the electric fields are expressed by implicit functional forms which are not suited to a conventional electron-trajectory analysis. This method is applied to parallel-plate and parallel-cylinder deflection systems.     

An electrostatic recording method using transformer assemblies based on error-correcting codes

A new high-speed electrostatic recording method has been developed that utilizes assemblies of transformers whose secondary windings are wound on the cores and connected to output terminals in arrangements based on (n,k) or fixed-weight error-correcting codes. This method is used to distribute electrostatic recording pulses to styli to form latent images on recording paper. With the present experimental device a recording speed of 480 kilodots per second, or 436 steps per second, was obtained.     

Calculation of electrostatic fields surrounding finite circular cylindrical conductors

Analytical expressions are derived for the calculations of electric potentials and fields surrounding circular cylinders of finite lengths. Results of several examples are presented.     

Modal fields calculation using the finite difference beampropagation method

A method is described to construct modal fields for an arbitrary one- or two-dimensional refractive index structure. An arbitrary starting field is propagated along a complex axis using the slowly varying envelope approximation (SVEA). By choosing suitable values for the step-size, one mode is maximally increased in amplitude on propagating, until convergence has been obtained. For the calculation of the next mode, the mode just found is filtered out, and the procedure starts again. The method is tested for one-dimensional refractive index structures, both for nonabsorbing and for absorbing structures, and is shown to give fast convergence     

Production of uniform electrostatic fields by a slotted conductingspherical shell

A spherical structure that specifies electric potential on a spherical surface to produce a uniform electric field near the center of the sphere is considered. The surface is divided on lines of constant latitude (polar angle), and the resulting bands are constrained to have particular voltages. The particular case of three conducting surfaces with voltages V₁, 0, and -V₁ is considered in detail. Polar angles are determined that give the required uniformity of the field     

Failure mode analysis of AlGaAs/GaAs HBTs using electrostatic discharge method

The failure modes of AlGaAs/GaAs heterojunction bipolar transistors (HBTs) showing increases of base leakage current found during the bias and temperature reliability test have been examined and analysed by using an electrostatic discharge (ESD) method. In the examination for HBT having an emitter of 2 × 20 μm, increases of a base leakage current have been observed when an ESD of around 100 V is applied through a base-emitter junction. Furthermore, increases of a collector leakage current have been observed with the additional ESD of around 150 V. Since no fatal effects for the transistor amplification are found in the high current region, the degradations are concluded to be responsible to the local damages of the base layer at the edge of base-emitter junction. Applying the Wunsch-Bell model to the damaged region, the temperature is estimated to be in a range from 400 to 550°C. It is thought that thermal destruction occurs in a base layer.     

Electric fields in the human body due to electrostatic discharges

Electrostatic discharges (ESDs) occur when two objects at different electric potentials come close enough to arc (spark) across the gap between them. Such discharges may be either single-event or repetitive (e.g., 60 Hz). Some studies have indicated that ESDs may be a causative factor for health effects in electric utility workers. Moreover, a hypothesis has recently been forwarded imperceptible contact currents in the human body may be responsible for health effects, most notably childhood leukemia. Numerical modeling indicates that the electric fields in human tissue resulting from typical contact currents are much greater than those induced from typical exposures to electric and magnetic fields at power line frequencies. Numerical modeling is used here to compute representative spark-discharge dosimetry in a realistic human adult model. The frequency-domain scalar potential finite difference method is applied in conjunction with the Fourier transform to assess electric fields in selected regions and tissues of interest in the body. Electric fields in such tissues as subcutaneous fat (where peripheral nerves may be excited), muscle and bone marrow are of the order of kilovolts per meter in the lower arm. The pulses, however, are of short duration (approximately 100 ns).     

Transient electric and magnetic fields associated with establishinga finite electrostatic dipole, revisited

The authors reexamine the analysis of M.J. Master and M.A. Uman (1983), who derived and plotted the electromagnetic field waveforms generated by a square wave of current propagating with constant speed along a finite linear path, resulting in the formation of a finite electrostatic dipole. It was concluded that such a square pulse of current had charge only at its front and rear. The authors argue that errors were made in that analysis, correct these errors, and extend the overall analysis: (1) to show that the decomposition of the electromagnetic fields into electrostatic, induction, and radiation components on the basis of distance dependence is not general; (2) to demonstrate the use of the continuity equation in finding the charge distribution along a current path when the current distribution is known; and (3) to show how a seemingly simple analytical technique, the treatment of an abrupt step of current as a linearly rising current in the limit that the risetime goes to zero, can lead to erroneous results if there is not a good physical and mathematical understanding of all the variables involved     

An iterative method for solving electrostatic problems

The method of steepest descent is applied to the solution of electrostatic problems. The relation between this method and the Rayleigh-Ritz, Galerkin's, and the method of least squares is outlined. Also, explicit error formulas are given for the rate of convergence for this method. It is shown that this method is also suitable for solving singular operator equations. In that case this method monotonically converges to the solution with minimum norm. Finally, it is shown that the technique yields as a by-product the smallest eigenvalue of the operator in the finite dimensional space in which the problem is solved. Numerical results are presented only for the electrostatic case to illustrate the validity of this procedure which show excellent agreement with other available data.     

Evaluation of interactions of electric fields due to electrostatic discharge with human tissue

Electrostatic discharges (ESDs) produce in the human tissue very strong electric fields of short duration. Possible biophysical interactions are evaluated by comparing the fields in subcutaneous fat/skin to the thresholds for peripheral nerve stimulation, and by computations of membrane potential and electric fields in cytoplasm of a typical cell in bone marrow. It is found that a 4-A peak ESD event is capable of stimulation of nerves located in subcutaneous fat of the lower arm of the hand eliciting a spark, with tens of kV/m and pulse duration of approximately 80 ns. For the same ESD event, the transmembrane potential (TMP) reaches 32 mV with a pulse duration of approximately 200 ns (half-width duration). The electric field in the cytoplasm of a bone marrow cell changes from about 8.8 kV/m to--2 kV/m in about 200 ns.     

Theoretical and experimental characterization of transientelectromagnetic fields radiated by electrostatic discharge (ESD)currents

The problem of the evaluation of the electromagnetic (EM) field radiated by an electrostatic discharge (ESD) current is examined, and an efficient numerical code for the evaluation of the radiated field is developed. The considered radiating structures, a monopole and a loop, are analyzed in the time domain using a modified electric field integral equation (EFIE). A modification of the integral equation was introduced in order to take into account the reflection of the incident pulse at the input terminals of the antenna, when fed by a transmission line. The reflected wave is very significant and its evaluation is fundamental for the comparison of theoretical and experimental data. The ESD current flowing along the wire is determined using the method of moments in time domain (MoMTD). From the knowledge of the transient current, the radiated EM field is evaluated by a standard technique. The developed model is the first stage of a project for the characterization of the measurement environment during an ESD test. All numerical results are validated by measurements and good agreement is shown     

Sampling electrostatic force probing using pulse positionmodulation technique

A sampling electrostatic force microscopy method utilising a pulse position modulation technique is demonstrated. High frequency arbitrary waveforms within integrated circuits are measured by down converting the high frequency spectrum of the circuit waveform to within the active frequency band of the mechanical frequency response of the probe     

The charge-density method of solving electrostatic field: Program and error analysis

The Charge-Density method of solving electrostatic field has many advantages over the finite difference or finite element method, but its accuracy and fitness are still in question. By direct evaluating electrical potentials, the errors along surface of the electrode are plotted, which are the maximum errors for an electrostatic problem. It is shown that higher accuracy will be reached if more sub-regions are chosen at where the charge density is high or at the region near the area where the field is to be calculated. This will be helpful to understand and use the method efficiently. It is more convenient and accurate to use the chargedensity method when we deal with the calculation of an electrostatic system having a great difference in size between electrodes (such as the point emitter diode). Using the information of error on the surface of electrode, we can estimate the potential errors in each calculation or rearrange the sub-regions to improve the accuracy of the next calculation. A program is set up. The difference between the calculated data and that of E. Harting and F. H. Read (1976) is less than 1%.     

Determination of time-of-flight surfaces using the method of moments [US imaging

To produce an image from backscattered signals requires a knowledge of the time of flight from each source to each sensor in a transducer array. The authors reduced the determination of the rectangular coordinates of a new point on any time-of-flight surface, which requires finding the square root of the sum of squares, to the time of a single addition. To do this, the time-of-flight surface was represented by a two-dimensional, positive-integer-degree polynomial and then that polynomial was implemented in its forward-difference form. Two solutions for such a polynomial were found using the method of moments. A minimum-mean-square-error constraint yields polynomial coefficients from a numeric evaluation of the moments of arbitrary surfaces over rectangular regions, and an analytical solution for moments of time-of-flight surfaces over sector-shaped regions. For a 7x6-cm region at a minimum range of 4 cm centered in a 74 degrees sector, the maximum error for a second-degree polynomial was 0.30% of the average time of flight over the region for the numeric solution and 0.32% for the analytic solution, assuming a 1500-m/s background velocity.     

Drop formation characteristics of electrostatic ink jet using water-based ink

Drop formation characteristics of electrostatic ink jets using water-based ink are reported. At first, to understand drop formation phenomena and processes, we took high-speed photographs. We investigated, using one capillary and kind of ink, ink-drop frequency versus ink-flow characteristics. From these characteristics, we calculated ink-drop diameters treating a drop as a sphere. Then, from these ink-drop frequency versus ink-drop diameter characteristics, we estimated attainable ink-drop frequencies and ink-drop diameters for a specific capillary. Lastly, comparisons were made among ink-drop frequency versus recorded-diameter characteristics for different capillaries, particularly their outside diameters.