Highly Sensitive Electromechanical Piezoresistive Pressure Sensors Based on Large-Area Layered PtSe₂ Films

Abstract

Two-dimensional (2D) layered materials are ideal for micro- and nanoelectromechanical systems (MEMS/NEMS) due to their ultimate thinness. Platinum diselenide (PtSe2), an exciting and unexplored 2D transition metal dichalcogenide material, is particularly interesting because its low temperature growth process is scalable and compatible with silicon technology. Here, we report the potential of thin PtSe2 films as electromechanical piezoresistive sensors. All experiments have been conducted with semimetallic PtSe2 films grown by thermally assisted conversion of platinum at a complementary metal–oxide–semiconductor (CMOS)-compatible temperature of 400 °C. We report high negative gauge factors of up to −85 obtained experimentally from PtSe2 strain gauges in a bending cantilever beam setup. Integrated NEMS piezoresistive pressure sensors with freestanding PMMA/PtSe2 membranes confirm the negative gauge factor and exhibit very high sensitivity, outperforming previously reported values by orders of magnitude. We employ density functional theory calculations to understand the origin of the measured negative gauge factor. Our results suggest PtSe2 as a very promising candidate for future NEMS applications, including integration into CMOS production lines.

PtSe 2 grown directly on polymer foil for use as a robust piezoresistive sensor

“…Additional SEM images at lower magnification are shown in Figure S1 The electromechanical properties of PtSe 2 on polyimide were tested by flexing the films while simultaneously measuring the films' resistance using a custom-made, three-point flexure rig, as detailed in the methods section. Under applied strain a decrease in resistance was observed, resulting in a negative gauge factor consistent with previous reports on other TMDs 21 , and also with previous experimental reports on PtSe 2 films transferred onto a bending-beam cantilever setup 23 . In previous reports on TMDs, the negative gauge factor has been attributed to an increase in the density of states and a decrease in the size of the bandgap under applied strain 21,23 .…”

Two‐Dimensional Noble‐Metal Chalcogenides and Phosphochalcogenides

“…A more scalable approach was reported by Yim et al., who employed thermally assisted conversion on a Si/SiO 2 substrate. This method is remarkable due to the low growth temperature of 400 °C, which allows polycrystalline PtSe 2 films with nanometer‐sized grains to be obtained in a fashion that is directly compatible with back‐end‐of‐line semiconductor processing.…”

“…Few‐layer PtSe 2 is semimetallic and the density of states at the Fermi level increases under strain, thereby giving rise to a large piezoresistive effect. This allowed Wagner et al . to construct highly sensitive pressure sensors based on 4.5 nm thick PtSe 2 membranes.…”

“…NMDCs gained a lot of attention as new members of the 2D family, since they showed a layer‐controllable metal‐to‐semiconductor transition, with few layers and the bulk phase featuring the topological properties of Dirac type‐II semimetals . The NMDCs also showed an outstanding performance as sensors, for example, for pressure or for specific molecular species . Their chemistry, which includes highly anisotropic structural features, low‐energy differences between different polymorphs, controllable phase changes, and catalytic properties, differs from that of the transition‐metal dichalcogenides (TMDCs), such as MoS 2 and WSe 2 .…”

Zweidimensionale Edelmetallchalkogenide und ‐phosphochalkogenide

“…NMDCs haben viel Aufmerksamkeit als neue Mitglieder der Familie von 2D‐Materialien erhalten, weil diese einen kontrollierbaren Metall‐zu‐Halbleiter‐Übergang mit der Lagenanzahl aufweisen, wobei dünne Schichten und das Bulk‐Material topologische Eigenschaften als Dirac‐Typ‐II‐Halbmetall besitzen . Die NMDCs zeigen eine herausragende Leistung als Sensoren, zum Beispiel für Druck oder bestimmte molekulare Spezies . Ihre Chemie, die sehr anisotrope strukturelle Merkmale, geringe Energiebarrieren zwischen den Strukturtypen, kontrollierbare Phasenübergänge und katalytische Eigenschaften beinhaltet, unterscheidet sich von den Übergangsmetalldichalkogeniden (TMDCs) wie MoS 2 oder WSe 2 .…”