In this research, we report a facile method for synthesizing a series of carboxyl functionalized graphene quantum dots (GQDs) using graphite flakes (300 meshes) as raw material. These highly luminescent GQDs emitted blue, light blue, green, yellow, and red light (400–700 nm intensity peaks) under ultraviolet irradiation conditions, while exhibiting quantum yields in the range of 50–70%. The products were comprehensively characterized using ultraviolet-visible, photoluminescence, infrared, Raman, and dynamic light scattering spectroscopies. The GQDs were found to remain highly stable against photobleaching when stored over a prolonged period of more than three months. The proposed method for the synthesis of high quality, multicolor GQDs can be utilized to extend the application of these nanoparticles to molecular biotechnology and bioengineering; for example, the immobilization of cancer markers on their surface. As such, carboxylic acid groups present on the surface of these GQDs help create complexes for in vivo sensing applications.

In this article, a charge-plasma (CP)-based gate-all-around (GAA) silicon vertical nanowire tunnel field-effect transistor (NWTFET) is proposed. The effects of interface trap charges (ITCs) on dopingless (DL) NW-based device have been addressed for the first time. CP technique is used to induce charge carriers within the drain/source regions by depositing layers of metals with specific work function. Linearity performance parameters such as higher order harmonic distortions (HDs), intermodulation distortions (IMDs), and interception points are calculated including the effects of ITCs on the cylindrical channel-surround gate-oxide interface. This work shows that positive ITCs can help in improving the device characteristics, whereas negative ITCs degrade the device performance. The ON-state current to OFF-state current ratio decreases for either polarity of ITCs. The ON-state current has been improved by approximately 50% with higher positive ITCs. The presence of positive ITCs in DL NWTFET improves the driving capability to be used for analog applications. The linearity parameters tend to improve with positive ITCs and degrade with negative ITCs. The proposed device has reached the same cutoff frequency at lower operating gate bias (approximately 0.8 V) with half the threshold voltage for higher positive ITCs.

In this paper, the structure of Core-Shell Junctionless Nanotube Tunnel Field Effect Transistor is proposed and investigated to minimize the fabrication steps and fabrication complexity of the device. The proposed junctionless device is implemented as a biosensor. The core-source metal and shell gate electrode are created using suitable work function. The p-type source region is created by using metal of work function 5.93eV and the shell gate is created by using a metal of work function 4.5eV, over the silicon surface. For biosensing application, a nano cavity is introduced between core source metal and source region. The device is vertically aligned which provides stability to the biomolecules within the structure. For the investigation of biosensing application, three biomolecules of different dielectric constants, streptavidin (k = 2.1), 3-aminopropyltriethoxysilane (k = 3.57), and protein (k = 8), are used. The performance of the device for biosensing application is analyzed for both neutral and charged biomolecules. To examine the efficiency of the device, various characteristics are studied based on parametric variations, the effect of charged biomolecules, and sensitivity of the device and so on. The motivation behind our work is to design a device having optimum performance attributes without sacrificing the performance parameters of the device such as the ON-state current, subthreshold slope, ION/IOFF ratio, etc.

In this article, two nanotube structures have been proposed: namely, core-shell dopingless nanotube tunnel field effect transistor (CS-DL-NT-TFET) and Si0.5Ge0.5 source CS-DL-NT-TFET. The application of charge-plasma (CP) technique in their designing offers a fabrication advantage, which is the elimination of doping. Performance analysis of the two nanotube structures has been carried out on the basis of RF and analog parameters such as their transconductance (gm), transfer characteristics (ID-VGS), output conductance (gds), output characteristics (ID-VDS), cut-off frequency (fT), and gate capacitance (Cgg). Furthermore, the two devices have also been investigated for linearity and reliability based on parameters such as higher-order transconductances (gm3 and gm2), distortions [second-order harmonic distortion (HD2)], interception points [third-order input interception point (IIP3), second-order voltage interception point (VIP2), and third-order voltage interception point (VIP3)], and intermodulation distortion [third-order intermodulation distortion (IMD3)]. Based on the analysis of different parameters, the Si0.5Ge0.5 source CS-DL-NT-TFET was observed to have achieved an improved performance as compared to its Si-source counterpart due to a lower energy bandgap, higher mobility, and lower tunneling mass. The proposed device is optimized to maintain the uniformity of the induced CP within the source/drain regions. The optimized architecture enhances the device performance by attaining an average subthreshold slope of 31.38 mV/dec with a higher ON-current.

A novel device architecture charge plasma-based Ring-TFET (CP-RingTFET) has been described in this work. The ring structure of the proposed device uses a core-shell architecture with a drain at the center covered with the channel and followed by the source. The ring structure has the advantage of ultrascaling and mechanical strength as compared to the nanowire structure. The performance characteristics of the Ring-TFET are much better as compared to nanowire-TFET with similar physical dimensions. To investigate the impact of charge plasma on RingTFET architecture, various analog and linearity parameters have been studied; such as off-state current (Ioff), on-state current (Ion), Ion/Ioff, subthreshold slope (SS), gate-to-gate capacitance, transconductance (gm), transconductance gain factor (TGF), threshold voltage (VTH), higher-order transconductances, higher-order harmonic distortions, third-order current intercept point (IIP3), third-order intermodulation distortions (IMD3), and higher-order voltage intercept points. The ability of the CP-RingTFET to enhance the performance of the proposed device is confirmed with the reduction of Ioff, improving Ion/Ioff, lower SS including the benefits of threshold voltage reduction.