Wednesday, November 29, 2017

Material Based “Field-Effect CCD”

Many old ideas are recycled with a new twist - in this case the twist is the new materials. paper "Two-dimensional material based "field-effect CCD" by Hongwei Guo, Wei Li, Jianhang Lv, Akeel Qadir, Ayaz Ali, Lixiang Liu, Wei Liu, Yiwei Sun, Khurram Shehzad, Bin Yu, Tawfique Hasan, and Yang Xu from Zhejiang University, China, State University of New York, USA, and University of Cambridge, UK says:

"In this work, we reported a novel detecting/imaging device concept called field-effect CCD (FECCD), which is based on CCD’s MOS photogate but requires no charge transfer between pixels (i.e. “couple”). The “couple” is re-defined as the capacitive coupling21,22 between the semiconductor substrate and the 2D material (e.g. graphene). In the semiconductor, we created the potential well for charge integration by applying a gate voltage pulse. In the 2D material, the non-destructive and direct readout along with the charge signal amplification was realized by the strong field effect.

Besides, the charge integration in our FE-CCD is beneficial for the low-light-level condition, and gives high linearity for accurate image capturing. The FE-CCD also shows a broadband response from visible to short-wavelength infrared (SWIR) wavelength, and its power consumption is readily suppressed by using the 2D-material hetero-junction.

Schematic of our FE-CCD pixel. The gate can be driven by fast
-sweeping or pulsed voltage. Holes (blue spheres) are generated
and integrated in the potential well with corresponding
electrons (red spheres) transferred to graphene.
(a) The proof-of-concept FE-CCD linear array working in both
random-access mode and charge transfer mode.
Top: the FE-CCD linear array wire-bonded to the printed-circuit board.
Bottom: the enlarged the optical image of the FE-CCD linear array.
Scale bar: 50 um.
(b, c) Reflection images at different integration time obtained
by scanning the single graphene-based FE CCD pixel under the
incandescent light (power density 5×10-5 W/cm2).

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