Test & Measurement

An Improved Method for Differential Conductance Measurements

As modern electronics continue to shrink, researchers are increasingly looking to nanotechnology as the basis for the next breakthrough in device size and power consumption. Indeed, as semiconductor structures are made smaller and smaller, the distinction between small silicon geometries and large molecules becomes blurred. Approached from either direction, the consequences are the same. Quantum behavior such as tunneling begins to play an important role in the electrical characteristics. In the macroscopic world, conductors may have obeyed Ohm’s Law (Figure 1a), but in the nanoscale, Ohm’s definition of resistance is no longer relevant (Figure 1b). Because the slope of the I-V curve is no longer a fundamental constant of the material, a detailed measurement of the slope of that I-V curve at every point is needed to study nanodevices. This plot of differential conductance (dG = dI/dV) is the most important measurement made on small scale devices, but presents a unique set of challenges.

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Gearing Up for Parametric Test’s High Voltage Future

Many parametric test engineers are learning to cope with new high voltage process requirements. Not surprisingly, high voltage processes require high voltage parametric testing for process control and reliability monitoring. Part of the challenge lies in the fact that these new high voltage requirements add to the list of parametric tests rather than replacing some portion of it. In many if not most cases, the high voltage transistors are controlled by complex logic that requires low voltage/low current parametric test. Consequently, both high voltage and logic tests have to be addressed within the same test plan while minimizing impact on throughput.

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Rapidly Expanding Array of Test Applications Continues to Drive Source Measurement Unit Instrument Technology

Since their introduction more than two decades ago, source measurement units (SMUs) have evolved into a category of multi-purpose instruments that are regularly called upon to address a rapidly expanding array of electronics industry applications:Semiconductor device fabrication, process development, and product research/design Production verification of electronic products such as portable wireless devices Production and development of new advanced materials for devices such as solar cells and HBLEDs Almost any electronic device test application

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A Mass-Spectrometer System for Detecting Gas Leaks

This versatile, expandable system can be controlled from a safe remote location. The Hydrogen Umbilical Mass Spectrometer (HUMS) consists of an integrated sample delivery system, a commercial mass-spectrometer- based gas analyzer, and a set of calibration gas mixtures traceable to NIST (National Institute for Standards and Technology). The system, except for the calibration gas mixtures and the remote operator display, fits into a standard 24-in. wide, 6-ft high, 36-in. deep (0.61 by 1.83 by 0.91 m, respectively) equipment rack and is powered by 120-Vac, 30-A, 60-Hz source. It was designed to perform leak detection and measurement of cryogenic propellants (oxygen and hydrogen) from a remote location during shuttle-launch countdown. It is used specifically to sample the background gas surrounding the 17-in. (0.43-m) Orbiter-ET disconnect, looking for leakage of gaseous hydrogen. The capability to monitor shuttle purge gases and cryogenic hydrogen fill and drain line T-0 disconnect helium purge gas is incorporated into the shuttle installation on each Mobile Launch Platform (MLP).

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Measuring Contact Angles of a Sessile Drop and Imaging Convection Within It

Ordinary and laser-shadowgraph images yield valuable information. Figure 1 depicts an apparatus that simultaneously and synchronously records magnified ordinary top-view video images and laser-shadowgraph video images of a sessile drop. The real-time values of contact angle and rate of evaporation of the drop as functions of time can be calculated from the apparent diameters of the drop in the sequences of the images. In addition, the shadowgraphs contain flow patterns indicative of thermocapillary convection (if any) within the drop. These time-dependent parameters and flow patterns are important for understanding the physical processes involved in the spreading of evaporating liquids in such diverse technological applications as coating (including painting), film cooling, processing of materials, lubrication, and boiling. Study of the spreading of drops can also contribute to understanding of the spreading of biological cells.

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Simulating the Structural Behavior of Laminated Glass

This report investigates the strength of archi- tectural laminated glass and the viability of its use for window glass in commercial buildings. Some researchers recommend that the structural behavior of laminated glass (typically consisting of two glass layers and a plasticized PVB [polyvinyl butyral] interlayer) is equivalent to the structural behavior of monolithic glass (one solid piece of glass) for most common applications. However, if this monolithic equivalency assumption is not valid, its implementation would result in the unconservative design and use of laminated glass, which could lead to failure of the glass at the design load. Using ALGOR Mechanical Event Simulation (MES) software, laminated and monolithic glass plates were modeled and analyzed to compare their response to a wind load. Stress results for the two plates were very different due to shear deformations experienced by the interlayer of the laminated plate. This research may help to ensure the safe use of laminated window glass.

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Pressure-Application Device for Testing Pressure Sensors

This device generates a pulse of known pressure. A portable pressure-application device has been designed and built for use in testing and calibrating piezoelectric pressure transducers in the field. The device generates pressure pulses of known amplitude. A pressure pulse (in contra- distinction to a steady pressure) is needed because in the presence of a steady pressure, the electrical output of a piezoelectric pressure transducer decays rapidly with time.

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