Diameter-Dependent Surface Photovoltage and Surface State Density in Single Semiconductor Nanowires

Soudi, Afsoon; Hsu, Cheng-Han; Gu, Yi

doi:10.1021/nl301863e

Cited by 59 publications

(61 citation statements)

References 37 publications

(55 reference statements)

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“…In addition to the usual characterisation of the deep traps in the semiconductor, an analytical model allows the measurement of the surface band-bending of a ZnO nanowire. These results corroborate data obtained using surface sensitive techniques such as ultraviolet photoelectron spectroscopy [16] and surface photovoltage measurements [17].…”

Section: Introductionsupporting

confidence: 89%

Current-mode deep level transient spectroscopy of a semiconductor nanowire field-effect transistor

Isakov

Sourribes

Warburton

2017

Journal of Applied Physics

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One of the main limiting factors in the carrier mobility in semiconductor nanowires is the presence of deep trap levels. While deep-level transient spectroscopy (DLTS) has proved to be a powerful tool in analysing traps in bulk semiconductors, this technique is ineffective for the characterisation of nanowires due to their very small capacitance. Here we introduce a new technique for measuring the spectrum of deep traps in nanowires. In current-mode DLTS (I-DLTS) the temperature-dependence of the transient current through a nanowire field-effect transistor in response to an applied gate voltage pulse is measured. We demonstrate the applicability of I-DLTS to determine the activation energy and capture cross-sections of several deep defect states in zinc oxide nanowires. In addition to characterising deep defect states, we show that I-DLTS can be used to measure the surface barrier height in semiconductor nanowires.

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Section: Introductionsupporting

confidence: 89%

Current-mode deep level transient spectroscopy of a semiconductor nanowire field-effect transistor

Isakov

Sourribes

Warburton

2017

Journal of Applied Physics

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“…[10][11][12][13][14][15][16][17][18][19][20][21] In particular, Kelvin probe force microscopy (KPFM) has been implemented to probe the electrical characteristics of a variety of PV materials and devices, ranging from organic materials [ 9,[22][23][24] and oxides [ 25 ] to III-V semiconductors for multijunction designs [26][27][28] and polycrystalline thin fi lms. [ 18,[29][30][31][32][33][34][35] The local optoelectronic properties and changes in material composition have also been mapped using near-fi eld scanning optical microscopy (NSOM) probes as local sources of excitation.…”

mentioning

confidence: 99%

Nanoimaging of Open‐Circuit Voltage in Photovoltaic Devices

Tennyson

Garrett

Frantz

et al. 2015

Advanced Energy Materials

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voltage and the overall electrical behavior of a device strongly depend on the nonradiative recombination rate of the charge carriers within a material, which is affected by the defects inherently present within the semiconductor. Despite all the efforts in developing higher performance thin-fi lm polycrystalline solar cells, such as CdTe, CuIn x Ga (1− x ) Se 2 (CIGS), and Cu 2 ZnSnS 4 (CZTS), the difference between the theoretically predicted and the best experimentally achieved V oc is still considerably large (up to 0.6 V). [ 2,3 ] For Si, extensive research has been dedicated to design and implement nanostructured light-trapping architectures to boost light absorption; [4][5][6][7] however, there are very few experiments showing how the V oc is affected. For organic PV blends, the limited V oc observed in most bulk heterojunction solar cells is attributed to geminate and nongeminate losses; [ 8,9 ] nevertheless, local variations in V oc have never been measured. Thus, for any micrometer-and nanoscale structured PV device, assessing variations in V oc with nanoscale resolution and spatially resolving where recombination occurs within the material can potentially change the pathway for designing higher performance devices.Imaging methods based on atomic force microscopy (AFM) techniques have been extensively used to characterize the structural and electrical properties of PV materials and full devices. [10][11][12][13][14][15][16][17][18][19][20][21] In particular, Kelvin probe force microscopy (KPFM) has been implemented to probe the electrical characteristics of a variety of PV materials and devices, ranging from organic materials [ 9,[22][23][24] and oxides [ 25 ] to III-V semiconductors for multijunction designs [26][27][28] and polycrystalline thin fi lms. [ 18,[29][30][31][32][33][34][35] The local optoelectronic properties and changes in material composition have also been mapped using near-fi eld scanning optical microscopy (NSOM) probes as local sources of excitation. [36][37][38][39][40][41][42] Very recently, photoluminescence has emerged as a promising tool to map charge recombination [43][44][45] and carriers diffusion [ 46 ] with high spatial resolution. At low temperature (70 K), photoluminescence imaging with submicrometer resolution has been implemented to map a 10 meV quasi-Fermi level splitting in CIGS solar cells, where variations in the intensity signal were attributed to changes in the material composition. [ 47 ] Nevertheless, none of these imaging techniques provide a direct measurement of V oc within the material at operating conditions. A straightforward, universal, and accurate method to measure the V oc (and hence nonradiative recombination processes) with high spatial resolution in PV materials is still missing.Here, we present a new imaging technique based on illuminated KPFM to map the V oc of optoelectronic devices with nanoscale resolution <100 nm. We map the contact potential difference (CPD) of half or fully processed solar cells in the For most photovoltaic (PV) devices, the...

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“…[1][2][3][4][5][6] When these species are adsorbed to the wire surface, charge transfer from the ZnO NW to the adsorbed species induces band bending that can appear as either an electron depletion layer or an electron accumulation layer. UV illumination or electron beam bombardment could break the bonds between the ZnO NW and the species 7,8) and could even create persistent conduction in ZnO wires. 5,[9][10][11] Surface-related phenomena and persistent photoconductivity may produce an additional conduction path (electron accumulation) or a reduced conduction section (electron depletion), making reliable measurement of the transport properties a challenge.…”

mentioning

confidence: 99%