Nonuniform Nanowire Doping Profiles Revealed by Quantitative Scanning Photocurrent Microscopy

Allen, Jonathan; Perea, Daniel E.; Hemesath, Eric R.; Lauhon, Lincoln J.

doi:10.1002/adma.200803865

Cited by 114 publications

(149 citation statements)

References 32 publications

(48 reference statements)

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“…This calculation indicates that the surface dopant concentration is enriched in the larger diameter n-Si NWs, although the NW FETs still behave as a heavily doped depletion mode devices after removal of this surface layer. The similar dopant surface segregation in an Ϸ60-nm diameter NWs has been reported recently on the basis of scanning photocurrent microscopy, transport measurement and atom probe tomography (19). In contrast, I-V g data recorded from devices with an Ϸ22-nm diameter single oxidation/etch and control NWs (Fig.…”

Section: Resultsmentioning

confidence: 88%

“…Direct experimental determination of dopant location in NWs is challenging, although there has been recent progress (17)(18)(19)(20)(21). For example, high-resolution secondary ion mass spectroscopy was used to probe for gold-impurities in m diameter Si wires with a depth resolution of Ϸ20 nm (17), and atom probe tomography has been used to investigate the distribution of impurity atoms in Si NWs with nanometer resolution (18,19). The vertical geometry needed for these latter measurements may, however, place limitations on growth conditions that yield NWs suitable for analysis.…”

mentioning

confidence: 99%

“…Theoretical studies suggest a tendency toward surface doping in molecular diameter p-and n-Si NWs (15,16) that are considerably smaller than structures used to fabricate most reported NW devices. Direct experimental determination of dopant location in NWs is challenging, although there has been recent progress (17)(18)(19)(20)(21). For example, high-resolution secondary ion mass spectroscopy was used to probe for gold-impurities in m diameter Si wires with a depth resolution of Ϸ20 nm (17), and atom probe tomography has been used to investigate the distribution of impurity atoms in Si NWs with nanometer resolution (18,19).…”

mentioning

confidence: 99%

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Diameter-dependent dopant location in silicon and germanium nanowires

Xie

Fang

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

108

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We report studies defining the diameter-dependent location of electrically active dopants in silicon (Si) and germanium (Ge) nanowires (NWs) prepared by nanocluster catalyzed vapor-liquidsolid (VLS) growth without measurable competing homogeneous decomposition and surface overcoating. The location of active dopants was assessed from electrical transport measurements before and after removal of controlled thicknesses of material from NW surfaces by low-temperature chemical oxidation and etching. These measurements show a well-defined transition from bulk-like to surface doping as the diameter is decreased <22-25 nm for nand p-type Si NWs, although the surface dopant concentration is also enriched in the larger diameter Si NWs. Similar diameterdependent results were also observed for n-type Ge NWs, suggesting that surface dopant segregation may be general for small diameter NWs synthesized by the VLS approach. Natural surface doping of small diameter semiconductor NWs is distinct from many top-down fabricated NWs, explains enhanced transport properties of these NWs and could yield robust properties in ultrasmall devices often dominated by random dopant fluctuations.nanoelectronics ͉ surface doping ͉ surface segregation ͉ vapor-liquid-solid growth

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Section: Resultsmentioning

confidence: 88%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Diameter-dependent dopant location in silicon and germanium nanowires

Xie

Fang

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

108

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“…Several experiments have probed the consequences of such defects on the spatial variation of photoresponse of nanostructures. [16,33,39,40,42,43] In these experiments, the effect of the defect is to create a local hill, or a valley, in the potential landscape. The photocarriers are generated in the same material that carries the charge carriers to the electrodes.…”

mentioning

confidence: 99%

“…We investigate the efficiency of these devices for photoconversion and attempt to understand the role of defects in modifying optoelectronic properties. [16] Prior to studying the hybrid devices, we probe individual WS 2 nanotubes and show that they offer a good optoelectronic platform. [17,18] We used WS 2 multiwalled * deshmukh@tifr.res.in † contributed equally nanotubes [8,19] obtained from NanoMaterials.…”

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confidence: 99%

Light matter interaction in WS₂ nanotube-graphene hybrid devices

et al. 2014

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We study the light matter interaction in WS2 nanotube-graphene hybrid devices. Using scanning photocurrent microscopy we find that by engineering graphene electrodes for WS2 nanotubes we can improve the collection of photogenerated carriers. We observe inhomogeneous spatial photocurrent response with an external quantum efficiency of ∼1% at 0 V bias. We show that defects play an important role and can be utilized to enhance and tune photocarrier generation.Heterostructure devices of transition metal dichalcogenides (TMDCs) and graphene have generated considerable research interest recently because of their superior optical and electronic properties.[1, 2] The semiconducting nature of TMDCs combined with the presence of van Hove singularities in their electronic density of states allows for efficient photon absorption and carrier generation under optical excitation.[3] Combining this feature with the high mobility of graphene has led to optoelectronic studies of heterostructure devices comprising graphene and single layer TMDCs. [1,[3][4][5][6][7] These devices have exhibited good quantum efficiency for photocurrent generation in the visible range. However, the fabrication of such heterostructures requires multiple exfoliation and transfer steps. TMDC nanotubes[8] represent another alternative for such applications; nanowires offer an additional advantage because they can enhance the absorption of light through the formation of optical cavities[9, 10] and quasi 1D structures are known to enhance light matter interaction by virtue of an enhanced joint density of states (JDOS).[11] Silicon and carbon nanotubes have been shown to be promising materials for solar-cell applications. [12,13] Similarly, TMDC nanotubes could also allow for large scale integration of on-chip optoelectronic elements. In addition, the curvature of the nanotubes can be used to engineer spin and valley based optoelectronic control in dichalcogenide systems.[14] Here, we investigate the photoresponse of WS 2 nanotubes with field-effect transistor geometry and the enhanced photoresponse properties of hybrid devices of WS 2 nanotubes with graphene electrodes. One of the motivations for using graphene electrodes for the nanotube is to modulate the density of carriers in the electrodes and modify the Schottky barrier;[15] the other motivation is to observe the spatial homogeneity of the photoresponse. We investigate the efficiency of these devices for photoconversion and attempt to understand the role of defects in modifying optoelectronic properties. [16] Prior to studying the hybrid devices, we probe individual WS 2 nanotubes and show that they offer a good optoelectronic platform. [17,18] We used WS 2 multiwalled * deshmukh@tifr.res.in

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Measuring the Electronic Properties of Materials at the Nanoscale

Lauhon

2012

Characterization of Materials

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The general objective of electronic property measurements is to relate extrinsic characteristics of devices or test structures to the intrinsic properties of materials. When there are significant nanoscale inhomogeneities in macroscale materials, or the materials themselves are nanoscale, the measurement of electronic properties at high spatial resolution may be essential to the fundamental understanding of structure–property relationships. This chapter is intended to serve as a framework for the consideration of measuring the electronic properties of materials at the nanoscale, and as a guide to the use of other articles in this volume. Background is provided on general principles of nanoscale measurement, approaches to nanofabrication that enable investigation of nanoscale and nanostructured materials, and distinct regimes of transport that inform the interpretation of electrical measurements. Specific techniques that exploit local probe–sample interactions are introduced according to their principles of operation, to either locally measure characteristics of a material or to generate a local perturbation material that is detected remotely. This framework is used to organize the chapter in terms operational mechanisms of techniques, rather than outcomes of measurement. Noncontact measurements that generate knowledge of local electronic properties are also examined. The chapter is not strictly limited to techniques that provide nanoscale resolution, but rather techniques that resolve electronic properties on length scales over which said properties may vary. The chapter focuses on generally accessible measurements of practical importance to understanding and optimizing the properties of materials with readily envisioned applications.

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Nonuniform Nanowire Doping Profiles Revealed by Quantitative Scanning Photocurrent Microscopy

Cited by 114 publications

References 32 publications

Diameter-dependent dopant location in silicon and germanium nanowires

Diameter-dependent dopant location in silicon and germanium nanowires

Light matter interaction in WS₂ nanotube-graphene hybrid devices

Measuring the Electronic Properties of Materials at the Nanoscale

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Nonuniform Nanowire Doping Profiles Revealed by Quantitative Scanning Photocurrent Microscopy

Cited by 114 publications

References 32 publications

Diameter-dependent dopant location in silicon and germanium nanowires

Diameter-dependent dopant location in silicon and germanium nanowires

Light matter interaction in WS2 nanotube-graphene hybrid devices

Measuring the Electronic Properties of Materials at the Nanoscale

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Product

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Light matter interaction in WS₂ nanotube-graphene hybrid devices