D.V. Kerns

Model for CMOS/SOI single-event vulnerability

A lumped-parameter model derived from transistor characterization data has been used in SPICE analyses to study and predict the single-event-upset thresholds for SIMOX SOI (separation by implantation of oxygen, silicon-on-insulator) SRAMs (static random-access memories) with a variety of cell designs. The modeling of CMOS/SOI transistors with fully bottomed sources and drains includes direct representation of the parasitic lateral bipolar structure. Results indicate that, in the SOI devices investigated, single events simulate a localized bipolar response, even in devices with bodies electrically tied to active nodes. The bipolar response enhances the destabilizing effect of an ion event. The total current impulse contributing to upset can be significantly greater than that produced by direct ionization within the hit transistor, i.e., devices can be upset by ions that deposit less than the total charge required to initiate logic state reversal. In light of this, advanced CMOS/SOI-SOS logic with short channel lengths (and therefore significant parasitic bipolar gain) may exhibit critical LETs (linear energy transfers) lower than expected from simple scaling rules, and thinning of the active regions may not significantly reduce single-event rates in such CMOS/SOI digital circuits. >

Temperature dependence and effect of series resistance on the electrical characteristics of a polycrystalline diamond metal‐insulator‐ semiconductor diode

Temperature dependency and the series resistance effect on the electrical characteristics of a polycrystalline diamond‐based (Au/Ti)/undoped‐diamond/doped‐diamond metal‐insulator‐ semiconductor Schottky diode were investigated in a temperature range 25–300u2009°C. The current‐voltage (I‐V) characteristics of the device show rectifying behavior with the forward bias conduction limited by series resistance. Over the temperature range investigated, the I‐V data confirmed that the conduction mechanism of the diode is controlled by thermionic field emission. Modifying the thermionic field emission equation to include the series resistance model allows the ideality factor and barrier height of the Schottky diode to be calculated. Temperature dependence of the ideality factor and apparent barrier height was determined. By extrapolating the forward saturation current data, the evaluated ideality factor was observed to decrease from 2.4 to 1.1 while the apparent barrier increased linearly from 0.68 to 1.02 eV in the t...

A study of diamond field emission using micro-patterned monolithic diamond tips with different sp2 contents

Electron field emission from an array of micro-patterned monolithic diamond tips with varying sp2 content has been systematically investigated. The experimental results show that the field emission characteristics can be improved and the turn-on electric field can be reduced more than 50% by increasing sp2 content. Two hypotheses are proposed as an explanation of the effect of sp2 content on the field emission characteristics of diamond tips: the lowering of the work function due to defect-induced band generated by sp2 content in the diamond lattice and an increase in the field enhancement factor due to embedded sp2–diamond–sp2 cascaded microstructures.

Photon generation by silicon diodes in avalanche breakdown

Light emission from a p-n diode biased in controlled avalanche breakdown has been measured over the photon energy range 1.4–3.4 eV. Previously published models are compared with measured data to associate specific mechanisms with avalanche photon emission in silicon. A multimechanism model fitting the measured spectrum is presented.

A new hydrogen sensor using a polycrystalline diamond-based Schottky diode

A new hydrogen sensor utilizing plasma-enhanced chemical vapor deposited diamond in conjunction with palladium (Pd) metal has been developed. The device is fabricated in a layered Pd/Undoped diamond/p-doped diamond Schottky diode configuration. Hydrogen sensing characteristics of the device have been examined in terms of sensitivity, linearity, response rate, and response time as a function of temperature and hydrogen partial pressure. Hydrogen adsorption activation energy is investigated in the temperature range from 27 to 85 C. Analysis of the steady-state reaction kinetics using the I-V method confirm that the hydrogen adsorption process is responsible for the barrier height change in the diamond Schottky diode. The ability to fabricate diamond-based hydrogen sensor on a variety of substrates makes the device very versatile for gas sensing.

Efficient electron emitter utilizing boron-doped diamond tips with sp2 content

Abstract A practical technique to enhance the electron emission of diamond tips by incorporation of boron dopant and sp 2 content is reported. The effects of boron doping on electron field emission from an array of micro-patterned polycrystalline pyramidal diamond microtips with varying sp 2 content have been systematically studied. The field emission characteristics of undoped and boron-doped diamond tips are significantly improved by increasing sp 2 content of diamond tips. By increasing sp 2 content, the turn-on electric field can be reduced more than 50% for both undoped and boron-doped diamond tips. Likewise, the turn-on electric field of the diamond tips with higher sp 2 content decreases substantially with boron doping. A new field emission mechanism, that is, an increase in the field enhancement factor due to hole accumulation via the formation of cascaded sp 2 -diamond-sp 2 embedded microstructures in diamond tips, is a possible explanation for the enhanced effects of boron doping and sp 2 content on the diamond field emission characteristics.

Diamond as an active sensor material

Abstract Diamond has attractive properties as an advanced electronic material. Its combination of high carrier mobility, electric breakdown, and thermal conductivity results in the largest calculated figures of merit for speed and power of any material. Previously (J.L. Davidson, W.P. Kang, Examples of diamond sensing applications, Proceedings 3rd International Symposium on Diamond Film (ISDF-3), Polytechnical Institute of Russian Academy of Science, St. Petersburg, Russia, 16–19 June 1996) we reported the discovery and development of useful ‘secondary’ effects in diamond and applying them to interesting sensor applications. For example, boron-doped diamond piezoresistors for strain micro-gauges on rugged MEMS (microelectromechanical structures) pressure and acceleration sensors. This paper will present some recent developments with chemically vapor-deposited diamond for microelectromechanical sensing applications such as a new design all diamond pressure microsensor that measures pressure at high temperatures and an accelerometer with over 45xa0kHz resonant frequency. Also, presented are recent results on layered diamond films that behave as chemical sensors measuring hydrogen, oxygen and many other chemicals’ concentration. For example, a diamond-based chemical gas sensor using Pt/SnO x /i-diamond/p + -diamond metal–insulator–semiconductor diode structure for oxygen sensing is described. In addition, the latest emission properties of fabricated diamond microtips for field emitters are reviewed.

Field emission enhancement of diamond tips utilizing boron doping and surface treatment

Abstract A practical field emission enhancement technique for diamond tips with sp 2 content utilizing boron doping and surface treatment, achieving a very low turn-on electric field of 1xa0V/μm, has been developed. The effects of surface treatment and boron doping on electron field emission from an array of micropatterned polycrystalline diamond microtips with sp 2 content have been systematically investigated. Regardless of doping, the field emission characteristics of diamond tips are significantly enhanced and the turn-on electric field is reduced more than 60% after surface treatment. Likewise, regardless of surface treatment, the turn-on electric field of the diamond tips with sp 2 content decreases substantially with boron doping. Possible mechanisms responsible for the field emission enhancement are an increase in the field enhancement factor due to hole accumulation via the formation of cascaded sp 2 –diamond–sp 2 embedded microstructures and field forming process with enhanced hole accumulation after surface treatment.

Diamond microelectronic gas sensors

Abstract Diamond-based microelectronic gas sensors using plasma enhanced chemical vapor deposition (PECVD) technology have been explored in our laboratory. This paper presents a new gas sensor using Pd/i-diamond structure for hydrogen detection. Hydrogen sensitivity of the device has been characterized and analyzed as a function of hydrogen partial pressure and temperature by using current-voltage (I–V) and capacitance-voltage-frequency (C-V-F) methods. The hydrogen sensitivity is high, reproducible, and repeatable over a wide temperature range including room temperature.

Polycrystalline diamond pressure microsensor

Abstract Diamond deposition processing and silicon photolithographic and etching techniques were used to create undoped diamond diaphragms a few millimetres in diameter and 5–10 microns thick. Delineated and electrically isolated doped diamond resistors nominally 100 microns wide by 500 microns long by 4 microns thick, with thick film silver-based interconnect are fabricated on top of the diaphragm. Zero strain values of the resistors are nominally a few hundred kΩ Isolation ratio is greater than 103. As the membrane is flexed by pressure, the ΔR R piezoresistance (PZR) of the diamond resistors was measured. Various PZR configurations and temperature behaviour were examined.