目前壓電式壓力感測器只能偵測單一種應力，成大材料系劉全璞講座教授團隊為全世界第一個利用壓電閘極(piezo-gating effect)發展可以偵測兩種應力模式的新穎壓電式壓力感測器。圖一呈現壓電閘極電晶體元件設計，利用一對上電極及一對下電極。在單一壓應力下，壓電電場會驅使載子沿著電場飄移，使元件同時操作在depletion及accumulation雙模式。為了解雙模式運作，研究團隊也發展了整套理論模型及運算，如圖二。圖三為在V_d=1V下，Drain current與應力在上下電極模式之實驗結果，可以第一次清楚看到隨應力愈大電流在depletion mode呈現減小，在accumulation mode增大的趨勢，並且與研究團隊的理論模擬結果吻合，世界最高的壓力感測靈敏度(Gauge Factor)高於2000。研究團隊以兩種不同載子濃度的元件討論載子濃度對此元件壓力感測靈敏度的影響，並且也詳細討論壓阻效應扮演次重要的角色。

eeNews Europe文章連結: https://www.eenewseurope.com/en/first-dual-mode-piezo-gated-transistor/
Nano Energy文章連結: https://doi.org/10.1016/j.nanoen.2022.106985


Fig. 1 (a) the top electrode-based devices & (b) the bottom electrode-based devices




Fig. 2 Schematics of the mechanism of piezotronic effect on positive c-axis oriented ZnO thin-film (a) Piezo-charge distribution under a compressive force on PGTFT, (b) Corresponding cross-sectional ideal band diagram showing the electrons are driven from the top surface to the bottom surface by the piezopotential. (c) the depletion region thickness varies along the y-axis with applied external bias (VDS) for top electrode-based PGTFT, (d) a similar phenomenon happens with accumulation region thickness under external bias for bottom electrode-based PGTFT.




Fig. 3 Comparison of the current under different load conditions between analytical and experimental results for the top electrode (a, b) and bottom electrode (c,d) of the samples AOZnO (a,c) and ArZnO (b,d). Comparison of the gauge factor between the experimental data and the calculated results for (e) top and (f) bottom_electrode-based devices.