Broadband alternating current photovoltaic effect: An application for high-performance sensing and imaging body aches

Kumar, Mohit; Choi, Hyobin; Lim, Jun Hee; Park, Jiyong; Kim, Sangwan; Seo, Hyungtak

doi:10.1016/j.nanoen.2020.105240

Cited by 22 publications

(41 citation statements)

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“…As further evidence of the Au‐dot‐size‐dependent Schottky barrier formation, Kelvin probe force microscopy (KPFM) measurements were conducted to collect nanoscale contact potential difference data ( V CPD ). [ 10,15,16 ] Interestingly, KPFM measurements revealed that the V CPD changed spatially, as shown in Figure 2e. This variation in V CPD was solely attributed to the size‐dependent work function of the Au dots because the electron affinity of bulk p ‐Si does not change spatially.…”

Section: Resultsmentioning

confidence: 94%

“…However, the noted spikes, particularly for centrosymmetricmaterial-based junctions, such as Au dot/Si, are new and have recently been revealed. [16,19] In fact, these spikes appear because of a new type of influence called the alternating current photovoltaic (AC-PV) effect, which occurs under periodic light illumination at the junction/interface of the materials. Indeed, rapid splitting and realignment of the quasi-Fermi levels owing to sudden changes in illumination conditions is the main reason for the occurrence of these peaks, which in turn oscillate the electrons (current) back and forth in the external circuit to maintain the potential difference between the two electrodes.…”

Section: Resultsmentioning

confidence: 99%

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Ultrafast Nanoscale Gradient Junction Self‐Powered Schottky Photodetectors for Vision‐Like Object Classification

Kumar

Lim

Park

et al. 2021

Advanced Optical Materials

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subsequently processing it using advanced electronic devices/circuits, has become the backbone of current artificial intelligence (AI) technology. [1][2][3] Traditionally, optical machine vision has been achieved by two fundamental but separate units, namely hardware (photosensor) that collects optical information and converts it into an electrical domain, and software (a well-defined mathematical algorithm) that post-processes this information. [3] Among them, the development of a highperformance photodetector is critical because it must detect the input optical signals instantly, almost effortlessly, and under self-power conditions, allowing it to meet the demand for quick and energy-efficient processing, particularly in time-crucial applications, such as pattern recognition. [4][5][6] Therefore, comprehensive research efforts have been dedicated to the development of self-powered photodetectors. [1,2,[5][6][7][8] To date, most of the efforts at developing high-performance photodetectors are based on the optimization of the junction built-in potential, efficient photo-absorption-induced charge collection, and reduced recombination rate. However, to this end, the remaining vital challenge is to develop large-area reproducible photodetectors that can operate at extremely low energy consumption levels, the most demanding of which is achieving self-power, which clearly requires the development of an alternative photodetector with a robust performance.An impressive alternative would be to develop a self-powered optoelectronic device that can inherently overcome the drawbacks of electronics in terms of energy efficiency, speed, and throughput. [7][8][9][10] Under this scenario, a photodetector operates based on the principle of an alternative photovoltaic effect (AC PV) that can provide the opportunity to achieve a robust photo response because the splitting and realignment of the quasi-Fermi level owing to a pulsed illumination can alter the effective charge transport, resulting in a new possibility of designing high-performance photodetectors. However, to the best of our knowledge, such an all-in-one platform with a robust optoelectronic performance has yet to be developed. Herein, we developed a nanoscale Schottky-junction-based broadband photodetector that can sense optical inputs under self-biased conditions. The photodetector operates based on the AC PV effect and demonstrates ultrafast rise/fall times of 30/400 ns at a wavelength of 365 nm. The nanoscale charge transport and photo response properties were revealed through photoconductive atomic force Emulating human vision for pattern classification is essential in intelligent machines, including pilotless vehicles and humanoid robots. Traditionally, analog visual information is captured by photosensors, which are sequentially classified using a physically separated algorithm-based unit, such as a computer. Among such units, a self-powered photodetector with a quick information sensing feature can be utilized for an unprecedented pattern classification; howeve...

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Section: Resultsmentioning

confidence: 94%

Section: Resultsmentioning

confidence: 99%

Ultrafast Nanoscale Gradient Junction Self‐Powered Schottky Photodetectors for Vision‐Like Object Classification

Kumar

Lim

Park

et al. 2021

Advanced Optical Materials

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“…substrates using an optimized large‐area sputtering technique at room temperature (RT), we performed sequential annealing at various temperatures (from 200 to 600 °C) under maintained oxygen environment, which resulted in the transformation of metallic films into a layer of metal oxide (for further details see the Experimental Section). [ 22 ] However, unlike traditional annealing, the samples were covered by a low resistive p‐Si (≈10 −3 Ω cm) wafer, which promotes the formation of densely packed and uniform layer of metal oxides on a wafer scale, resulting in a high‐performing device, as described below. Initially, the crystalline nature of metal oxide (i.e., TiO 2 ) grown at 200 and 600 °C was investigated using cross‐sectional transmission electron microscopy (TEM).…”

Section: Resultsmentioning

confidence: 99%

Ultrahigh‐Speed In‐Memory Electronics Enabled by Proximity‐Oxidation‐Evolved Metal Oxide Redox Transistors

et al. 2022

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of the most promising choices for future nonvolatile memory storage and neuromorphic circuit design. [6,7] Reversible, and ultrafast drifting of oxygen ions through an electric-field-induced redox process, so-called conductive filaments, is proposed as a fundamental process causing the resistance change in transition metal oxide-based memristive devices. [6,[8][9][10] Although redox-based two-terminal memristive devices have demonstrated significant success, they are still pinned down to a number of drawbacks as failing to achieve crucial features of in-memory processing such as high device conductance, achieving well-controlled multilevel memory/forgetting, long-term stability, and scalability over a large scale, all of these restrict the reliability and energy efficiency of the devices. [1,[6][7][8]11,12] In contrast, a multi-terminal solid-state resistive switching device, in which the redox process can be performed precisely by the gate, could offer an alternate platform for filament-less ultrafast memory storage and processing units. Until now, several redox based multi-terminal electronics have also been reported; for instance, Fuller et al. demonstrate parallel programming with an ionic floating-gate memory array and demonstrate its application to scalable neuromorphic computing with a microsecond operating speed. [13] Indeed, the operating speed of most of the reported redoxbased electronics is limited to the micro-or millisecond. [14][15][16] Therefore, there has yet to be a successful implementation of such a high-performing redox-based multi-terminal device and its integration over a large scale, which will, in fact, pave the way for hitherto unrevealed circuit capabilities.More importantly, current state-of-the-art nanoelectronics are confronting with major challenges of a substantial drop in computing performance as a discrepancy between the data handling speeds of processors and memories, referred to as the "memory wall," continues to widen. [1,7,12,[17][18][19][20] This makes the exploration of the integration of analog signal processing with memory operation even more essential. In this scenario, brain-inspired in-memory computing with conceptually new device architectures is emerging paradigm that have a potential to dramatically reduce the energy cost and capabilities, indeed, beyond the von Neumann architectures. [1,7,18,21] All the reports on inmemory-processing are noteworthy; however, none of these devices is capable of operating at ultrahigh processing rates;The pursuit of a universal device that combines nonvolatile multilevel storage, ultrafast writing/erasing speed, nondestructive readout, and embedded processing with low power consumption demands the development of innovative architectures. Although thin-film transistors and redoxbased resistive-switching devices have independently been proven to be ideal building blocks for data processing and storage, it is still difficult to achieve both well-controlled multilevel memory and high-precision ultrafast processing in a single unit, even ...

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“…Remarkably, photo-current (I ph = I light − I dark ) at 0 V increases gradually with light intensity, consisting of the fact that photo-generated e-h pairs density has a straight association to the photon absorption (see Figure 2b). [14,15] Additionally, the I ph variation with light intensity is used to estimate the linear dynamic range (LDR), which is one of the figures of the merit of the device. Mathematically, the LDR is express as 20 log[I ph /I dark ], where I dark is the dark currents and found 103 dB, indicating the excellent sensitivity toward the illuminating light.…”

Section: Resultsmentioning

confidence: 99%

“…The observed I dc is owing to typical photovoltaic effect; however, noticed spikes, especially for centrosymmetric materials, like Si, are new and revealed recently only. [15,20] In fact, these spikes appear because of a new kind of influence, named the alternating current photovoltaic effect, which becomes effective with periodic light illumination at the junction/interface of materials. Indeed, rapid splitting and realignment of quasi-Fermi levels with a sudden change in the light illuminating conditions is the key source behind these peaks, which in turn oscillates electrons (current) back and forth in the external circuit to maintain the potential difference between two electrodes.…”

Section: Resultsmentioning

confidence: 99%

Controllable, Self‐Powered, and High‐Performance Short‐Wavelength Infrared Photodetector Driven by Coupled Flexoelectricity and Strain Effect

et al. 2021

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This induced internal polarization field, in response, could redistribute the concentration of free carriers within semiconductors and at its contact interface, thereby changes the overall charge transport behavior, indeed analogous to the piezoelectric effect. [1,5] Importantly, strain gradient is the key to the flexoelectric effect; however, applied strain, in principle, will also modulate the electronic structure, which in turn could introduce conceptually innovative and till "forbidden" functionalities. [1,4,6] For instance, applied strain-induced broken crystal symmetry modify the effective masses of charge carriers, which leads to generating a pronounced shift in the effective bandgap of semiconductors, like silicon, TiO 2 , and others. [7][8][9] In fact, theoretically, it has been predicted that the fundamental bandgap of the silicon could be shrunk considerably (up to 1800 nm, e.g., short-wavelength infrared) with strain engineering. [9] As a basic building block, silicon is widely used in the microelectronics industry; however, owing to its fundamental optical bandgap (1.12 eV), the use of silicon for optoelectronics (including photovoltaics) is still limited to visible and near-infrared spectral range (λ ≤ 1100 nm). Indeed, the key challenge is to enlarge the broadband photoabsorption (up to short-wavelength infrared) of silicon, such that it can be applied for commercial application: however, this yet remained a critical challenge.Recently, distinct from the p-n junction-based photovoltaic effect (PV), the flexoelectric effect driven zero-bias photocurrent under light illumination has been demonstrated, known as the flexo-photovoltaic (FPV) effect. [6] Therefore, being universal property, strain gradient induced FPV effect and simultaneously modification of the effective bandgap exceeds the fundamental bandgap absorption limit not only for silicon but other class of semiconductors as well. However, the flexoelectric-driven photo response is still reported to the fundamental bandgap modification. Herein, we demonstrate that a photon sensing of the single crystal silicon is extended far beyond the fundamental bandgap by utilizing the flexoelectric effect. Particularly, the localized force applied by a pointed tip induces long-range distributed inhomogeneous strain, which not only breaks the centrosymmetry but also extend the fundamental Mechanical deformation-induced strain gradients and coupled spontaneous electric polarization field in centrosymmetric materials, known as the flexoelectric effect, can generate ubiquitous mechanoelectrical functionalities, like the flexo-photovoltaic effect. Concurrently, nano/micrometer-scale inhomogeneous strain reengineers the electronic arrangements and in turn, could alter the fundamental limits of optoelectronic performance. Here, the flexoelectric effect-driven self-powered giant shortwavelength infrared (λ ≤ 1800 nm) photoresponse from centrosymmetric bulk silicon, indeed far beyond the fundamental bandgap (λ = 1100 nm) is demonstrated. Particularly, large on/off...

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Broadband alternating current photovoltaic effect: An application for high-performance sensing and imaging body aches

Cited by 22 publications

References 50 publications

Ultrafast Nanoscale Gradient Junction Self‐Powered Schottky Photodetectors for Vision‐Like Object Classification

Ultrafast Nanoscale Gradient Junction Self‐Powered Schottky Photodetectors for Vision‐Like Object Classification

Ultrahigh‐Speed In‐Memory Electronics Enabled by Proximity‐Oxidation‐Evolved Metal Oxide Redox Transistors

Controllable, Self‐Powered, and High‐Performance Short‐Wavelength Infrared Photodetector Driven by Coupled Flexoelectricity and Strain Effect

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