Controlled Doping of Wafer‐Scale PtSe₂ Films for Device Application

Abstract

Semiconductive transition metal dichalcogenides (TMDs) have been considered as next generation semiconductors, but to date most device investigations are still based on microscale exfoliation with a low yield. Wafer scale growth of TMDs has been reported but effective doping approaches remain challenging due to their atomic thick nature. In this work, we report the synthesis of wafer-scale continuous few-layer PtSe 2 films with effective doping in a controllable manner. Chemical component analyses confirm that both n-and pdoping can be effectively modulated through the controlled selenization process. We systematically study the electrical properties of PtSe 2 films by fabricating top-gated field effect transistors (FETs). The device current on/off ratio is optimized in two-layer PtSe 2 FETs, and four-terminal configuration displays a reasonably high effective field effect mobility (14 and 15 cm 2 V -1 s -1 for p-and n-type FETs, respectively) with a nearly symmetric p-and n-type performance. Temperature dependent measurement reveals that the variable range hopping is dominant at low temperature. To further establish the feasible application based on controllable doping of PtSe 2 , a logic inverter and vertically stacked p-n junction arrays are demonstrated. These results validate that PtSe 2 is a promising candidate among the family of TMDs for future functional electronic applications.

Quantum confinement-induced semimetal-to-semiconductor evolution in large-area ultra-thin PtSe2 films grown at 400 °C

“…4b is 230, which is higher than previous reports for room temperature operation of PtSe 2 devices with channel thickness values in the range 2.5-3 nm. 13,17 The same characteristic in semi-log scale is shown in Supplementary Fig. 8a.…”

“…Considering the total resistance R tot = V DS /I DS ≈ 3.4 × 10 6 Ω at a given back-gate bias of V GS = 0 V, we obtain a large contact resistance of R c = (R tot -R ch )/2 ≈ 1.65 × 10 6 Ω compared to the channel resistance; hence, the actual voltage drop across the channel would be V ch ≈ 0.03 V. Using V ch instead of V DS in the g m equation, we obtain µ FE ≈ 10 cm 2 /V·s, which is close to the value obtained from Hall analysis and comparable to reported mobility for CVD-grown films. 17 It is important to note that the corrected µ FE value of ≈10 cm 2 /V·s is only an indicative value at the given V GS since the channel and contact resistances are expected to vary with the gate field. The polycrystalline nature of our synthesized PtSe 2 films could be another origin of the relatively low mobility compared to previously reported values of 7-210 cm 2 /V·s obtained from mechanically exfoliated PtSe 2 flakes.…”

“…PtSe 2 films grown on sapphire substrate by CVD at 500°C was recently reported indicating how the doping type of the films can be modified by the stoichiometry of the PtSe 2 films by a rapid or slow cool down process, which modifies the Se precursor supply. 17 In ref., 18 1 ML to 22 ML PtSe 2 films have been grown on bilayer graphene/6H-SiC (0001) substrates by molecular beam epitaxy, which in principle could be extended to grow large size films on dielectric substrates.…”

Recent progress in devices and circuits based on wafer-scale transition metal dichalcogenides

“…Compared with the strategy of combining two different TMDs together, it's more promising for practical application to obtain n-and p-type channels on the same TMD film, similar to that of conventional CMOS technology. For TMDs with a small band gap that exhibit ambipolar behavior, realization of both n-and p-type FETs has been demonstrated through chemical doping on channel region [28] or choosing different contact metals [12,102,103]. Table 2 including voltage gain and the supply voltage.…”

“…In order to move TMD based devices from laboratory studies to industrial circuit-level applications, it is more imperative to develop a scalable synthesis method to achieve high-quality, wafer-scale and continuous film. Thus it is essential to develop reliable and controllable synthetic strategy such as chemical vapor deposition (CVD) [25][26][27][28], molecular beam epitaxy (MBE) [29][30][31], metal-organic CVD (MOCVD) [32,33], and atomic layer deposition (ALD) [34,35]. During the past decade, researchers have made great achievements in the preparation of large-scale and high-quality 2D-TMDs samples via the CVD method, which greatly accelerate their practical application.…”