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Transconductance Amplification in Dirac-Source Field-Effect Transistors Enabled by Graphene/Nanotube Hereojunctions
摘要： Steep-slope devices are predicted to provide excellent quality for analog integrated circuit applications due to their high transconductance efficiency (gm/Ids) breaking the metal-oxide-semiconductor field-effect transistor limit (38.5 V?1). The potential advantage of a Dirac-source FET (DSFET) as an analog transistor is explored based on a graphene/carbon nanotube (CNT) heterojunction. A high gm/Ids beyond 38.5 V?1 over four decades of current is experimentally demonstrated in an individual CNT-based DSFET, reaching a peak value of 66 V?1, which is a new record for all reported transistors. Importantly, this high gm/Ids extends beyond the subthreshold region and leads to transconductance amplification in the overthreshold region. The best peak transconductance at a low bias of ?0.1 V exceeds 20 μS per tube, which has approximately threefold improvement over that of a normal CNT FET with a shorter gate length. Outperforming other advanced devices, the extended high transconductance efficiency greatly promotes DSFET competitiveness in the high-precision analog field.
关键词： carbon nanotubes,heterojunctions,Dirac sources,graphene,field-effect transistors
更新于2025-09-23 15:21:01
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Functionalized graphene transistor for ultrasensitive detection of carbon quantum dots
摘要： Ubiquitous carbon nanomaterials have great potential for emerging technologies, but they also pose a threat to human health at the end of their lifecycle, especially when they are introduced into waste or ground waters. Graphene field-effect transistors (GFET) and real time in situ confocal Raman microscopy (CRM) were employed to detect a submonolayer of carbon quantum dots (CQDs) in water. An effective GFET channel was formed on exfoliated and chemical vapor deposited (CVD) graphene. The adsorption of CQDs was monitored by measuring conductance changes in GFETs. The graphene channel was functionalized with (3-aminopropyl) triethoxysilane (APTES), which allowed for easy observation of a shift in the charge neutrality point (CNP) when the graphene channel was exposed to CQDs. The affinity of the CQD’s carboxyl terminal groups to the aminofunctionalized channel enabled a highly sensitive CQD detection based on changes in the GFET conductivity. The adsorption of the CQDs induced a positive shift of the CNP with a limit of detection at concentrations of 239 ppm and 62 ppm for the exfoliated and CVD graphene, respectively. A supporting study of graphene functionalization and CQD adsorption was performed by real time in situ CRM, ellipsometry, and ex situ X-ray photoelectron spectroscopy.
关键词： graphene field-effect transistors,carbon quantum dots,confocal Raman microscopy,chemical vapor deposited graphene,aminofunctionalized channel
更新于2025-09-12 10:27:22