In all nanodevices, zigzag carbon nanotubes (ZCNTs) and armchair-edge graphene nanoribbons (A-GNRs) serve as carbon-based channels for CNT- and GNR-based (T)FETs, as shown in left and right figures, respectively [
41
,
42
]. It is worth indicating that coaxial gate configurations (left figures) and double gate configurations (right figures) have been adopted for CNT- and GNR-based devices, respectively [
39
,
40
,
41
,
42
,
43
,
44
]. Note that our study encompasses FET and tunnel FET modes. Additionally, the DL-TFET is not a combination of the Schottky barrier and tunnel FETs because it lacks a Schottky junction between the electrically doped source and the CNT/GNR [
46
].
Figure 1
a,b present lengthwise cut views of the conventional Gate-All-Around (GAA) CNT(T)FET and Double Gate (DG) GNR(T)FET, respectively. These devices feature SiO
2
gate dielectrics and n-i-n or p-i-n chemical doping profiles [
45
,
47
]. The control gate covers the intrinsic channel region for both devices.
Figure 1
c,d showcase the proposed vacuum gate dielectric doping-free CNT(T)FET and GNR(T)FET, respectively. As their names suggest, these devices operate under dielectric-less [
27
,
28
,
29
] and doping-free [
46
] paradigms. Electrostatic control is utilized to achieve the doping profile necessary for FET and TFET operation via electrical source and drain doping gates.
Figure 1
e,f offer lengthwise cut views of the two proposed vacuum devices, revealing the absence of a bulk dielectric material around the channel, which is entirely controlled electrostatically, while 2D dielectrics can conceptually be adopted to cover the carbon channels forming metal-vacuum-2D dielectric-carbon structure, which is beneficial than MOS structure for radiation hardness. Notably, the CNT- and GNR-based vacuum devices are fully reconfigurable and can operate as FETs, TFETs, or BTBT FETs depending on applied biasing conditions (doping and control).
Figure 1
g,h present cross-sectional views perpendicular to the carbon-based channel. In the case of the CNTFET, even the inner environment of the CNT is considered a vacuum, which offers benefits in terms of immunity against radiation effects.
Table 1
provides details of the proposed designs, encompassing configuration, structure, and physical, dimensional, and electrical parameters of the vacuum nanodevices. It is important to note that this information and parameters are nominal, and any changes for parametric investigation’s sake will be explicitly highlighted.
