skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


Title: Intrinsic Photoconductivity of few-layered ZrS2 Phototransistors via Multiterminal Measurements
We report intrinsic photoconductivity studies on one of the least examined layered compounds, ZrS2.Few-atomic layer ZrS2 field-effect transistors were fabricated on the Si/SiO2 substrate and photoconductivity measurements were performed using both two- and four-terminal configurations under the illumination of 532 nm laser source. We measured photocurrent as a function of the incident optical power at several source-drain (bias) voltages. We observe a significantly large photoconductivity when measured in the multiterminal (four-terminal) configuration compared to that in the two-terminal configuration. For an incident optical power of 90 nW, the estimated photosensitivity and the external quantum efficiency (EQE) measured in two-terminal configuration are 0.5 A/W and 120%, respectively, under a bias voltage of 650 mV. Under the same conditions, the four-terminal measurements result in much higher values for both the photoresponsivity (R) and EQE to 6 A/W and 1400%, respectively. This significant improvement in photoresponsivity and EQE   in the four-terminal configuration may have been influenced by the reduction of contact resistance at the metal-semiconductor interface, which greatly impacts the carrier mobility of low conducting materials. This suggests that photoconductivity measurements performed through the two-terminal configuration in previous studies on ZrS2 and other 2D materials have severely underestimated the true intrinsic properties of transition metal dichalcogenides and their remarkable potential for optoelectronic applications.  more » « less
Award ID(s):
1900692
PAR ID:
10142805
Author(s) / Creator(s):
; ; ; ; ; ; ; ; ; ; ;
Date Published:
Journal Name:
Semiconductor Science and Information Devices
Volume:
1
Issue:
2
ISSN:
2661-3212
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; ; ; ; ; ; ; ; ; et al (, Nanoscale)
    null (Ed.)
    Among the layered two dimensional semiconductors, molybdenum disulfide (MoS 2 ) is considered to be an excellent candidate for applications in optoelectronics and integrated circuits due to its layer-dependent tunable bandgap in the visible region, high ON/OFF current ratio in field-effect transistors (FET) and strong light–matter interaction properties. In this study, using multi-terminal measurements, we report high broadband photocurrent response ( R ) and external quantum efficiency (EQE) of few-atomic layered MoS 2 phototransistors fabricated on a SiO 2 dielectric substrate and encapsulated with a thin transparent polymer film of Cytop. The photocurrent response was measured using a white light source as well as a monochromatic light of wavelength λ = 400 nm–900 nm. We measured responsivity using a 2-terminal configuration as high as R = 1 × 10 3 A W −1 under white light illumination with an optical power P opt = 0.02 nW. The R value increased to 3.5 × 10 3 A W −1 when measured using a 4-terminal configuration. Using monochromatic light on the same device, the measured values of R were 10 3 and 6 × 10 3 A W −1 under illumination of λ = 400 nm when measured using 2- and 4-terminal methods, respectively. The highest EQE values obtained using λ = 400 nm were 10 5 % and 10 6 % measured using 2- and 4-terminal configurations, respectively. The wavelength dependent responsivity decreased from 400 nm to the near-IR region at 900 nm. The observed photoresponse, photocurrent–dark current ratio (PDCR), detectivity as a function of applied gate voltage, optical power, contact resistances and wavelength were measured and are discussed in detail. The observed responsivity is also thoroughly studied as a function of contact resistance of the device. 
    more » « less
  2. ; ; ; ; ; ; ; ; ; ; et al (, Journal of Materials Chemistry C)
    null (Ed.)
    A wide variety of two-dimensional (2D) metal dichalcogenide compounds have recently attracted much research interest due to their very high photoresponsivities (R) making them excellent candidates for optoelectronic applications. High R in 2D photoconductors is associated to trap state dynamics leading to a photogating effect, which is often manifested by a fractional power dependence (γ) of the photocurrent (I ph ) when under an effective illumination intensity (P eff ). Here we present photoconductivity studies as a function of gate voltages, over a wide temperature range (20 K to 300 K) of field-effect transistors fabricated using thin layers of mechanically exfoliated rhenium diselenide (ReSe 2 ). We obtain very high responsivities R ~ 16500 A/W and external quantum efficiency (EQE) ~ 3.2 x 10 6 % (at 140 K, V g = 60 V and P eff = 0.2 nW). A strong correlation between R and γ was established by investigating the dependence of these two quantities at various gate voltages and over a wide range of temperature. Such correlations indicate the importance of trap state mediated photogating and its role in promoting high photo responsivities in these materials. We believe such correlations can offer valuable insights for the design and development of high performance photoactive devices using 2D materials. 
    more » « less
  3. ; ; ; ; ; ; ; ; (, Applied Physics Letters)
    This work reports the quantification of rise in channel temperature due to self-heating in two-terminal SrSnO3 thin film devices under electrical bias. Using pulsed current–voltage (I–V) measurements, thermal resistances of the thin films were determined by extracting the relationship between the channel temperature and the dissipated power. For a 26-nm-thick n-doped SrSnO3 channel with an area of 200 μm2, a thermal resistance of 260.1 ± 24.5 K mm/W was obtained. For a modest dissipated power of 0.5 W/mm, the channel temperature rose to ∼176 °C, a value which increases further at higher power levels. Electro-thermal simulations were performed which showed close agreement between the simulated and experimental I–V characteristics both in the absence and presence of self-heating. The work presented is critical for the development of perovskite-based high-power electronic devices. 
    more » « less
  4. ; ; ; ; ; (, Journal of Materials Chemistry C)
    High-performance hybrid graphene photodetectors were prepared with endohedral fullerenes deposited on graphene using electrophoretic methods for the first time. Endohedral Sc 3 N@C 80 , which acts as an electron acceptor, was used and the ensuing electronic and optoelectronic properties were measured. Another endohedral fullerene, La@C 82 , was also adsorbed on graphene, which acts as an electron donor. Upon optical illumination, for the Sc 3 N@C 80 –graphene hybrid, the photoinduced free holes are injected into graphene, increasing the hole carrier concentration in graphene, while the photoexcited electrons remain in Sc 3 N@C 80 ; this leads to a high photoresponsivity  of ∼10 9 A W −1 , detectivity D of ∼10 15 Jones, and external quantum efficiency EQE ∼ 10 9 % for the Sc 3 N@C 80 –graphene hybrid. This  is ∼10 times higher compared to other reports of quantum dot-graphene and few layer MoS 2 –graphene heterostructures. Similarly, for the La@C 82 –graphene hybrid,  ∼ 10 8 A W −1 , D ∼ 10 14 Jones, and EQE ∼ 10 6 % were achieved, with electrons being injected into graphene. The exceptional performance gains achieved with both types of hybrid structures confirms the potential of endohedrals to dope graphene for high performance optoelectronic devices using a facile and scalable fabrication process. 
    more » « less
  5. ; ; (, Advanced Optical Materials)
    Abstract Here, a wavelength‐specific photo‐thermoelectric (PTE) device is reported that achieves narrowband optical absorption and thermoelectric conversion functions using a stack of thin films on a grating‐patterned substrate. Conventional PTE devices are broadband with the absorption of electromagnetic radiation from ultraviolet to terahertz. There are demands for PTE devices that can exhibit narrowband response at a desired wavelength. Here, the narrowband PTE device consists of a photonic crystal (PC) filter with metal cladding and a thin‐film thermocouple. The PC‐PTE design is investigated numerically to illustrate the underlying energy conversion mechanism. The device is fabricated using nanoreplica molding followed by coating of thin films. The fabricated metal‐cladding PC resonator exhibits a narrowband optical absorption with a resonant absorption coefficient of 85.4% and full‐width‐half‐maximum of 14.8 nm in the visible wavelength range. The PTE measurements show that the thermoelectric output is sensitive to the coupling of incident light and guided‐mode resonance modes. Illuminated under the resonant condition, the PTE device exhibits a responsivity and noise equivalent power of 0.26 V W−1and 7.5 nW Hz−1/2, respectively. This PC‐PTE technology has the unique attributes of narrowband detection, large surface area, and low cost for the potential application in sensors, optical spectroscopy, and imaging. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email