The Moisture Dependence of the Electrical Sheet Resistance of Aluminum Oxide Thin Films with Application to Integrated Moisture Sensors
The measurement of moisture inside integrated circuit packages for reliability purposes involves either destructive mass spectroscopic tests, measurement of the impedance between interdigitated electrode pairs, or measurement of the capacitance of a parallel plate capacitor with a porous upper electrode and a dielectric of anodized aluminum oxide. This paper reports the use of an integrated circuit that combines interdigitated electrodes with a pair of matched field-effect transistors to permit sensitive, quantitative measurement of the moisture dependence of the sheet resistance of very thin filmis of oxidized aluminum. Data analysis is based on an equivalent circuit model for the device. It is found that the room temlperature sheet resistance of a 1500 Å film varies from 2 × 1015 Ohms/sq. at an ambient dew point of ¿43°C to 2 × 1010 Ohms/sq. at a dew point of +22°C. The device retains useful sensitivity below dew points of ¿60°C, and because of the absence of a porous upper electrode, exh ibits rapid response to changes in ambient moisture. Fabrication details, reproducibility, hysteresis, and aging of these devices is discussed.
The role of the MOS structure in integrated sensors
Abstract The basic properties of the MetalOxideSemiconductor (MOS) structure are reviewed with attention to the separation of electrochemical effects from charge-imaging effects. Two basic classes of sensors are identified: chemical sensors, which respond to changes in the chemical potential of a charged species within the gate structure, and charge sensors, which combine the charge-imaging property of the MOS structure with a property-dependent coupling element. The chemical sensors discussed include ion-sensitive field-effect devices, ion-controlled diodes and transition-metal-gate gas sensors. Charge sensors include charge-coupled imaging devices, charge-flow transistors, piezoelectric-gate strain sensors and membrane and/or beam-based capacitors for pressure and acceleration measurement.
Endodontic regeneration: hard shell, soft core
A loss of organs or the destruction of tissue leaves wounds to which organisms and living things react differently. Their response depends on the extent of damage, the functional impairment and the biological potential of the organism. Some can completely regenerate lost body parts or tissues, whereas others react by forming scars in the sense of a tissue repair. Overall, the regenerative capacities of the human body are limited and only a few tissues are fully restored when injured. Dental tissues may suffer severe damage due to various influences such as caries or trauma; however, dental care aims at preserving unharmed structures and, thus, the functionality of the teeth. The dentin–pulp complex, a vital compound tissue that is enclosed by enamel, holds many important functions and is particularly worth protecting. It reacts physiologically to deleterious impacts with an interplay of regenerative and reparative processes to ensure its functionality and facilitate healing. While there were initially no biological treatment options available for the irreversible destruction of dentin or pulp, many promising approaches for endodontic regeneration based on the principles of tissue engineering have been developed in recent years. This review describes the regenerative and reparative processes of the dentin–pulp complex as well as the morphological criteria of possible healing results. Furthermore, it summarizes the current knowledge on tissue engineering of dentin and pulp, and potential future developments in this thriving field.