Enhanced photocurrent response speed in charge-density-wave phase of TiSe2-metal junctions

• Published in: Nanoscale Vol. 13; no. 27; pp. 11836 - 11843
• Main Authors: Walmsley, Thayer S, Xu, Ya-Qiong
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 21.07.2021
• Subjects: Carrier mobility; Charge density waves; Cooling rate; Current carriers; Electrical junctions; Electronic devices; Optoelectronic devices; Phase transitions; Photoelectric effect; Photoelectric emission; Response time; Room temperature; Temperature dependence; Titanium; Transition metal compounds; Transition temperature
• ISSN: 2040-3364; 2040-3372
• DOI: 10.1039/d1nr01810h

Group IVB transition metal dichalcogenides (TMDCs) have attracted significant attention due to their predicted high charge carrier mobility, large sheet current density, and enhanced thermoelectric power. Here, we investigate the electrical and optoelectronic properties of few-layer titanium diselenide (TiSe2)-metal junctions through spatial-, wavelength-, temperature-, power- and temporal-dependent scanning photocurrent measurements. Strong photocurrent responses have been detected at TiSe2-metal junctions, which is likely attributed to both photovoltaic and photothermoelectric effects. A fast response time of 31 μs has been achieved, which is two orders of magnitude better than HfSe2 based devices. More importantly, our experimental results reveal a significant enhancement in the response speed upon cooling to the charge-density-wave (CDW) phase transition temperature (TCDW = 206 K), which may result from dramatic reduction in carrier scattering that occurs as a result of the switching between the normal and CDW phases of TiSe2. Additionally, the photoresponsivity at 145 K is up to an order of magnitude higher than that obtained at room temperature. These fundamental studies not only offer insight for the photocurrent generation mechanisms of group IVB TMDC materials, but also provide a route to engineering future temperature-dependent, two-dimensional, fast electronic and optoelectronic devices.