Supil Raina

P2.14: Characterization of the thermionic electron emission properties of nitrogen-incorporated “ridged” nanodiamond for use in thermal energy conversion

The thermal electron emission of “ridged” type nanocrystalline diamond films has been characterized for use in thermal energy conversion via thermionic emission.

High temporal resolution electrochemical biosensor using nitrogen-incorporated nanodiamond ultra-microelectrode array

Biosensors for detecting/measuring/monitoring the concentration of neurotransmitters that vary at sub-second time-scale can be achieved by using an electrode with high temporal resolution and fast electron transfer kinetics. Neurotransmitters, such as dopamine, undergo rapid fluctuations in concentrations occurring at a sub-second time scale. Real-time monitoring and measurement of these concentrationn changes, in-vivo or in-vitro, requires the use of ultra-microelectrode array (UMEA). This work reports on the development of a reliable UMEA electrochemical biosensor which can be used to identify, quantify, and monitor essential bio-analytes such as dopamine (DA), ascorbic acid (AA) and uric acid (UA) by using CVD nitrogen-incorporated nanodiamond UMEA without the need of electrode surface functionalization or modifications, making real-time detection possible. The application of fast-scan voltammetry (FSCV) for detecting dopamine and interfering bio-chemicals, including ascorbic acid and uric acid in 0.1M PBS (pH 7.4) by the UMEA has been realized. The detailed experiential method for the sensor array fabrication, and the UMEA sensitivity, selectivity, and detection limit for the detection of bio-analytes will be discussed.

A monolithic multi-finger nanodiamond lateral vacuum microtriode

This article reports a vacuum multi-finger monolithic microtriode utilizing nanodiamond as the emitting material. The structure is comprised of 140-fingerlike nanodiamond emitters with built-in nanodiamond gate and Si anode. A mixed lithography patterning approach is used to fabricate the three-terminal device structure. Triode characteristics, demonstrating gate controlled emission current modulation at low operating gate and anode voltages, are obtained. The realization of the efficient monolithic microtriode allows further development of robust vacuum integrated circuit for application in high temperature and radiation harsh environments.

Vacuum field emission integrated differential amplifier

This paper reports the development of an integrated vacuum field emission transistor differential amplifier (diff-amp) utilizing nanodiamond emitters. The device was fabricated by a dual-mask self-aligned mold transfer technique using standard silicon microfabrication technique in conjunction with chemical vapor deposited nanodiamond. The emission current of the transistor pair was validated by the Fowler-Nordheim equation. Well-matched field emission transistor characteristics and large common-mode rejection ratio of 55 dB were obtained, suggesting the capability of the device to reject common-mode noises and to amplify the information contained in differential signals.

Enhanced electron-field emission from nanodiamond ridge-structured emission arrays capped on micropatterned silicon pillars

In this article, the authors report the fabrication and observation of electron-field emission from nanodiamond ridge structure array capped on micropatterned silicon pillars. The fabrication process began with a deposition of 1.5-μm-thick ridge-structured diamond on a highly conductive n-type silicon substrate using microwave-plasma-enhanced-chemical-vapor deposition followed by patterning and reactive-ion etching techniques to get the device structure, which is an array of 50×50 silicon pillars capped with ridge-structured nanodiamond. Scanning electron microscope image confirms the device structure. The electron-field emission, performed in vertical-diode configuration, demonstrated a low threshold turn-on field of 1.2 V/μm and a high emission current of 150 μA at the anode field of 5.5 V/μm. The emission behavior has been compared with that of planar film of identical nanodiamond morphology. A 6000 times increase in current density is observed and attributed to its better geometrical-enhancement factor.

Nanodiamond macro- and microelectrode array bio-sensor

A thin-film nanodiamond macro-electrode and a microelectrode array (MEA) with SiO2 film as the insulator, both on a highly doped Silicon substrate were fabricated for biosensing applications. Fe(CN)3−/4−6 redox couple is used for electrochemical characterization of the MEA using cyclic voltammetry, which gives a sigmoidal response consistent with hemispherical diffusion limited mass transport mechanism. Using the nanodiamond MEA, we were also able to detect different concentrations of Dopamine in Phosphate Buffered Saline (pH 7.4) without any surface functionalization. The cyclic voltammograms show a steady state response and a linear relationship between the limiting current and Dopamine concentration. In contrast, the nanodiamond macro-electrode shows a peak shaped response due to semi-infinite linear diffusion of the analytes. Overall, the nanodiamond MEA has a larger analyte flux and thereby larger current density by virtue of its small area as compared to the macro-electrode making it more sensitive for detection of dopamine and other bio-analytes.

Nanodiamond vacuum field emission microtriode

Vacuum field emission (VFE) microtriodes utilizing nanodiamond emitters, integrated with a self-aligned silicon gate and an anode and fabricated by the mold-transfer patterning technique on a silicon-on-insulator (SOI) substrate, have been developed. The nanodiamond VFE microtriodes were fabricated by an integrated circuit-compatible microfabrication process in conjunction with chemical vapor deposition of nanodiamond into the inverted-pyramidal molds micropatterned on the SOI substrate, which provides precision controlled emitter-gate alignment and spacing. The devices exhibited triode characteristics showing anode field induced electron emission with gate controlled emission current modulation at low operating voltages, agreeing with its electron emission transport model. A high current density of 150 mA/cm2 is achievable from the device with the anode-emitter spacing of 4 μm at low operating voltages of Va = 48.5 V and Vg = 5 V. The ac characteristics of the microtriodes for signal amplification were e...

Implementation of nanodiamond field emission microelectronic integrated devices and circuits

This article reviews recent development of the vertically configured vacuum field emission integrated devices utilizing nanodiamond microtip emitters and their further implementation into circuits. The device design, fabrication and characterization of the nanodiamond vacuum field emission functional devices including transistor and triode are discussed. The realization of the basic circuit building block - differential amplifier - is also reported, indicating the feasibility of vacuum-based ICs. These developments provide a promising method for accomplishing vacuum-based microelectronics.

Vacuum microtriode utilizing nanodiamond microtip emitters

This article reports a vacuum field emission microtriode utilizing nanodiamond as the emitting material. The device was fabricated by IC-compatible fabrication process involving a mold transfer technique coupled with nanodiamond chemical vapor deposition. Triode behavior was characterized, showing gate-controlled emission current modulation with high current density at low bias conditions. A high current density of ~150 mA/cm2 is achievable at low operating gate and anode voltages. It was found the nanodiamond microtriode can be used as a buffer amplifier for high frequency applications. The realization of an efficient vacuum microtriode achieves a fundamental step for further development of vacuum integrated microelectronics.

Nanodiamond vacuum field emission triode signal amplifier

This paper presents the triode behavior of a gated nanodiamond vacuum field emitter array and its application in signal amplification. The triode feature is demonstrated with the observation of gate modulation on the emission current induced by the anode field. The emission characteristics are studied by considering the resultant electrical field on emitters, confirming the gate modulation effect. The voltage gain is examined, showing a reasonable value of 6.7 at the operating current of 50 μA. Higher gain is attainable at elevated operation currents.