Graphene nanowalls in photodetectors

Abstract

Graphene nanowalls (GNWs) have emerged as a promising material in the field of photodetection, thanks to their exceptional optical, electrical, mechanical, and thermodynamic properties. However, the lack of a comprehensive review in this domain hinders the understanding of GNWs' development and potential applications. This review aims to provide a systematic summary and analysis of the current research status and challenges in GNW-based photodetectors. We begin by outlining the growth mechanisms and methods of GNWs, followed by a discussion on their physical properties. Next, we categorize and analyze the latest research progress in GNW photodetectors, focusing on photovoltaic, photoconductive, and photothermal detectors. Lastly, we offer a summary and outlook, identifying potential challenges and outlining industry development directions. This review serves as a valuable reference for researchers and industry professionals in understanding and exploring the opportunities of GNW materials in photodetection.

Fig. 1. Photodetectors based on GNWs. Copyright © 2021, American Chemical Society. Copyright © 2017, Royal Society of Chemistry. Copyright © 2018, De Gruyter.

Fig. 2. Growth mechanism of GNWs. (a) Dissociation of carbon–hydrogen bonds by plasma; (b) formation of the buffer layer; (c) nucleation of vertical graphene; (d) growth of GNWs.

Fig. 3. Growth process of GMWs. (a) Schematic diagram of RF-PECVD equipment for the growth of GNWs. (b) Schematic illustrating the preparation process of GNWs.

Fig. 4. SEM images of GNWs with different growth time. (a)–(d) Top-view images; (e)–(h) cross-sectional images.

Fig. 5. TEM images and Raman spectra of GNWs. (a) Low magnification; (b) high magnification. (c) SAED pattern of the area indicated by white circle in MLG nanowalls; Copy right © 2012, Elsevier Ltd. (d) Raman spectra of GNWs and graphene film; Raman spectrum of MLG nanowalls grown for 60 min excited by (e) 633 nm and (f) 514 nm lasers. Copy right © 2012, Elsevier Ltd.

Fig. 6. Absorption spectra of GNWs with different growth time. (a) Transmittance; (b) absorbancy; (c) optoelectronic properties of the DLC interlayer with different thicknesses before and after annealing. Copyright © 2021, American Chemical Society.

Fig. 7. Sheet resistance (a) and conductivity (b) of GNWs; (c) plots of absorption curves calculated from the Tauc method for DLC film with different thicknesses; (d) band gap of DLC films with different thicknesses with and without annealing; Copyright © 2021, American Chemical Society. (e) The conductivity of a GNWs/Si and a GNWs/UVA hybrid film. © 2022 Elsevier B.V. All rights reserved. (f) Nyquist plots of EIS spectra recorded for the GWs and CdS-GWs (160 cycles) electrodes under the visible-light illumination (100 mW cm⁻²), in the electrolyte of 0.1 M Na₂S. Copyright © 2015 Elsevier B.V.

Fig. 8. Interface adhesion between GNWs and silicon substrate. (a) Cross-sectional SEM image of Si/GNWs; (b) micropattern of Si/GNWs. (c) and (d) high-magnification cross-sectional TEM images of Si/DLC/GNWs. Copyright © 2021, American Chemical Society.

Fig. 9. Energy band structure of GNWs/Si. (a) Uncontacted; (b) contacted; (c) schematic diagram of energy band structure of GNWs/Si heterojunction. Copyright © 2019, American Chemical Society.

Fig. 10. GNWs-based photovoltaic detectors. (a) Schematic representation of the GNWs/Si heterojunction detector structure; (b) illustration of the energy band diagram of the device; (c) device response under 8–14 μm laser excitation; (d) photocurrent response of the device at varying optical power levels; (e) response time characteristics of the device; (f) noise current associated with the device. Copyright © 2017, Royal Society of Chemistry.

Fig. 11. GNWs-based photovoltaic detectors. (a) Schematic illustration of the GNW heterostructure device grown on Si via PECVD; (b and c) device response at different wavelength bands; Copyright © 2019, AIP Publishing (d) schematic representation of the Si/Au/GNWs heterojunction device, incorporating Au nanoparticles on Si before the PECVD growth of GNWs; (e) variation in the device's absorption rate before and after the addition of Au; (f)–(i) photoresponse performance of the Si/Au/GNWs heterojunction detector. Copyright © 2019, American Chemical Society.

Fig. 12. GNWs-based photovoltaic detectors (a) fabrication process of GNWs using the PEALD method; (b) schematic illustration of the device structure; (c)–(f) photoelectric detection performance of the device; Copyright © 2021, American Chemical Society (g) schematic representation of the 3D-Gr/2D-Gr/Ge heterojunction detector structure; (h) photoelectric response currents of the 3D-Gr/2D-Gr/Ge heterojunction detector at various 1550 nm light power levels; (i) response time of the 3D-Gr/2D-Gr/Ge heterojunction detector. Copyright © 2020, American Chemical Society.

Fig. 13. Photogating effect of low dimensional materials. (a) Photocarriers in the photosensitive layer entering the conductive channel; (b) photocarriers in the photosensitive layer gathering at the interface; (c) influence of source–drain bias voltage on photocurrent; (d) influence of gate voltage on photocurrent.

Fig. 14. Photogating effect of GNWs/semiconductor heterojunction. (a) Dark current under an external bias due to intrinsic carriers in GNWs; (b) incident photons generate electron–hole pairs in the silicon; (c) these injected carriers gate the GNWs channel; (d) at the end of their lifetime, these carriers recombine back into silicon.

Fig. 15. GNWs-based photoconductive detectors. (a) and (b) Schematic diagram of optoelectronic detector device structures using GNWs on different Si substrates; (c) photoresponse of the three devices; Copyright © 2020 Elsevier Ltd. All rights reserved. (d) Schematic diagram of the VOG/Ge heterojunction photodetector. (e) UV-NIR absorption spectra of VOG/Ge and GQDs/VOG/Ge. (f) Photoresponse properties of the GQDs/VOG/Ge device under irradiation with light of 1550 nm with variable light intensities. The applied bias is 1 V. Copyright © 2020, American Chemical Society.

Fig. 16. GNWs-based photoconductive detectors. (a) and (b) Device structure and energy band diagram of photoconductive devices prepared by growing GNWs on SnO₂ film; (c) photoresponse performance of SnO₂/GNWs devices; Copyright © 2018 Elsevier B.V. (d) Schematic diagram of FET device structure directly grown GNWs on SnO₂ insulating layer substrate using PECVD; (e) photocurrent (I_ph) of the GNWs photodetector at various gate voltages; (f) time-dependent I_ph measurements of the GNWs photodetector and MLG photodetector working at their respective Dirac point voltage under the illumination of a 1550 nm laser, V_SD = 100 mV. Reprinted with permission from Copyright © The Optical Society.

Fig. 17. GNWs-based photoconductive detectors. (a) Schematic representation of Si/DLC/GNWs heterostructure device; (b) transformation of DLC layer to graphene-like structure after annealing; (c) infrared detection capability of Si/DLC/GNWs heterostructure device; Copyright © 2021, American Chemical Society. (d) Schematic of perovskite/GNWs photodetector device; (e) and (f) photoresponse performance of perovskite/GNWs photodetector device. Image source: “Lateral Structured Phototransistor Based on Mesoscopic Graphene/Perovskite Heterojunctions” (https://www.mdpi.com/2079-4991/11/3/641) by [Dahua Zhou*, Leyong Yu, Peng Zhu, Hongquan Zhao, Shuanglong Feng and Jun Shen] published under the Creative Commons Attribution License (CC BY) by MDPI. (g) Schematic view of the conformal graphene/SiNHs detectors. (h) Schematic view of the conformal graphene/SiNHs (i) measured photoresponse of the planar graphene/Si, SiNHs, and conformal graphene/SiNH detectors. Copyright © 2019, American Chemical Society.

Fig. 18. GNWs-based photothermal detector. (a)–(c) Schematic diagram of the thermal response of GNWs/PDMS composites. Copyright © 2018, De Gruyter (d)–(f) surface morphology change of GNWs film under different temperature from 25 to 90 °C. AFM image of cracks evolution on GNWs film (50 × 50 μm) (g)–(i) the AFM cross-section of crack region (3 μm). Copyright © 2011, RSC Publishing.

Fig. 19. GNWs-based photothermal detector. (a) Emissivity of GNWs/VO₂ devices at different GNWs deposition times (S1 = 5 min, S2 = 10 min, S3 = 15 min, S4 = 20 min, S5 = 25 min); (b) sheet resistance values of devices at different GNWs deposition times; (c) TCR and sheet resistance of optimized thickness device; Copyright © 2020 The Chinese Ceramic Society. Production and hosting by Elsevier B.V. (d)–(f) Photoresponse properties of photodetectors based on GNWs/PDMS composites; Copyright © 2018, De Gruyter. (g) The photocurrent of the GNWs/UVA detector underdifferent bias voltages at the wavelength of 8 μm at room temperature; (h) the photocurrent of the GNWs/UVA detector under different wavelengths from 8–10 μm before dripping; (i) the photocurrents of the GNWs/UVA detector under different wavelengths from 8–10 μm after dripping. Copyright © 2022 Elsevier B.V. All rights reserved.