Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userImaging electric field dynamics with graphene optoelectronics
68
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
The use of electric fields for signalling and control in liquids is widespread, spanning bioelectric activity in cells to electrical manipulation of microstructures in lab-on-a-chip devices. However, an appropriate tool to resolve the spatio-temporal distribution of electric fields over a large dynamic range has yet to be developed. Here we present a label-free method to image local electric fields in real time and under ambient conditions. Our technique combines the unique gate-variable optical transitions of graphene with a critically coupled planar waveguide platform that enables highly sensitive detection of local electric fields with a voltage sensitivity of a few microvolts, a spatial resolution of tens of micrometres and a frequency response over tens of kilohertz. Our imaging platform enables parallel detection of electric fields over a large field of view and can be tailored to broad applications spanning lab-on-a-chip device engineering to analysis of bioelectric phenomena.
rate research
Read More
The ability to perform nanoscale electric field imaging of elementary charges at ambient temperatures will have diverse interdisciplinary applications. While the nitrogen-vacancy (NV) center in diamond is capable of high-sensitivity electrometry, demonstrations have so far been limited to macroscopic field features or detection of single charges internal to diamond itself. In this work we greatly extend these capabilities by using a shallow NV center to image the electric field of a charged atomic force microscope tip with nanoscale resolution. This is achieved by measuring Stark shifts in the NV spin-resonance due to AC electric fields. To achieve this feat we employ for the first time, the integration of Qdyne with scanning quantum microscopy. We demonstrate near single charge sensitivity of $eta_e = 5.3$ charges/$sqrt{text{Hz}}$, and sub-charge detection ($0.68e$). This proof-of-concept experiment provides the motivation for further sensing and imaging of electric fields using NV centers in diamond.
We study photodetection in graphene near a local electrostatic gate, which enables active control of the potential landscape and carrier polarity. We find that a strong photoresponse only appears when and where a p-n junction is formed, allowing on-off control of photodetection. Photocurrents generated near p-n junctions do not require biasing and can be realized using submicron gates. Locally modulated photoresponse enables a new range of applications for graphene-based photodetectors including, for example, pixilated infrared imaging with control of response on subwavelength dimensions.
We use magnetic-field-dependent features in the photoluminescence of negatively charged nitrogen-vacancy centers to measure magnetic fields without the use of microwaves. In particular, we present a magnetometer based on the level anti-crossing in the triplet ground state at 102.4 mT with a demonstrated noise floor of 6 nT/$sqrt{text{Hz}}$, limited by the intensity noise of the laser and the performance of the background-field power supply. The technique presented here can be useful in applications where the sensor is placed closed to conductive materials, e.g. magnetic induction tomography or magnetic field mapping, and in remote-sensing applications since principally no electrical access is needed.
Terahertz field induced photocurrents in graphene were studied experimentally and by microscopic modeling. Currents were generated by cw and pulsed laser radiation in large area as well as small-size exfoliated graphene samples. We review general symmetry considerations leading to photocurrents depending on linear and circular polarized radiation and then present a number of situations where photocurrents were detected. Starting with the photon drag effect under oblique incidence, we proceed to the photogalvanic effect enhancement in the reststrahlen band of SiC and edge-generated currents in graphene. Ratchet effects were considered for in-plane magnetic fields and a structure inversion asymmetry as well as ratchets by non-symmetric patterned top gates. Lastly, we demonstrate that graphene can be used as a fast, broadband detector of terahertz radiation.
Semiconductor nanowire field-effect transistors represent a promising platform for the development of room-temperature (RT) terahertz (THz) frequency light detectors due to the strong nonlinearity of their transfer characteristics and their remarkable combination of low noise-equivalent powers (< 1 nW/Hz$^{1/2}$) and high responsivities (> 100 V/W). Nano-engineering a NW photodetector combining high sensitivity with high speed (sub-ns) in the THz regime at RT is highly desirable for many frontier applications in quantum optics and nanophotonics, but this requires a clear understanding of the origin of the photo-response. Conventional electrical and optical measurements, however, cannot unambiguously determine the dominant detection mechanism due to inherent device asymmetry that allows different processes to be simultaneously activated. Here, we innovatively capture snapshots of the photo-response of individual InAs nanowires via high spatial resolution (35 nm) THz photocurrent nanoscopy. By coupling a THz quantum cascade laser to scattering-type scanning near-field optical microscopy (s-SNOM) and monitoring both electrical and optical readouts, we simultaneously measure transport and scattering properties. The spatially resolved electric response provides unambiguous signatures of photo-thermoelectric or bolometric currents whose interplay is discussed as a function of photon density and material doping, therefore providing a route to engineer photo-responses by design.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
