Nonuniform doping distribution along silicon nanowires measured by Kelvin probe force microscopy and scanning photocurrent microscopy

Koren, Elad; Rosenwaks, Y.; Allen, Jonathan; Hemesath, Eric R.; Lauhon, Lincoln J.

doi:10.1063/1.3207887

Cited by 87 publications

(92 citation statements)

References 18 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…thermal evaporation of contact metals) 50,52,53 are only applicable to a certain range of microwire diameters, and are not compatible with many microwire/polymer structures, due to the complexity of the interactions between Fig. 4 Measured I-V data for a 100 mm long CH 3 -terminated (a) p-type and (b) n-type Si microwire with a diameter z 1.5 mm aligned at the PEDOT:PSS:Nafion/glass border, in dark and under solar AM 1.5G illumination.…”

Section: Discussionmentioning

confidence: 99%

Comparison between the electrical junction properties of H-terminated and methyl-terminated individual Si microwire/polymer assemblies for photoelectrochemical fuel production

Yahyaie

Ardo

Oliver

et al. 2012

Energy Environ. Sci.

View full text Add to dashboard Cite

The photoelectrical properties and stability of individual p-silicon (Si) microwire/ polyethylenedioxythiophene/polystyrene sulfonate:Nafion/n-Si microwire structures, designed for use as arrays for solar fuel production, were investigated for both H-terminated and CH 3 -terminated Si microwires. Using a tungsten probe method, the resistances of individual wires, as well as between individual wires and the conducting polymer, were measured vs. time. For the H-terminated samples, the n-Si/polymer contacts were initially rectifying, whereas p-Si microwire/polymer contacts were initially ohmic, but the resistance of both the n-Si and p-Si microwire/polymer contacts increased over time. In contrast, relatively stable, ohmic behavior was observed at the junctions between CH 3 -terminated p-Si microwires and conducting polymers. CH 3 -terminated n-Si microwire/polymer junctions demonstrated strongly rectifying behavior, attributable to the work function mismatch between the Si and polymer. Hence, a balance must be found between the improved stability of the junction electrical properties achieved by passivation, and the detrimental impact on the effective resistance associated with the additional rectification at CH 3 -terminated n-Si microwire/polymer junctions. Nevertheless, the current system under study would produce a resistance drop of $20 mV during operation under 100 mW cm À2 of Air Mass 1.5 illumination with high quantum yields for photocurrent production in a water-splitting device. Broader contextPhotoelectrosynthetic splitting of water to store solar energy in the simplest chemical bond, H-H, would provide a globally scalable means of compensating for the intermittency of solar energy at a given region of the earth's surface. A working device will require: a light harvesting component; redox catalysts; and a membrane barrier, for separating the products of the oxidation and reduction reactions, while maintaining efficient ionic conductivity to maintain charge neutrality. Given the useable solar energy range and the energy requirements for both oxidation and reduction reactions, it is challenging to find a single light absorber that can function efficiently. As in the natural photosynthetic system, it is possible to combine two light absorbers across a product-separating, ionically conductive membrane; however, the membrane is then required to manage, with minimal resistance, electron transport between the two light absorbers. We report herein the photoelectrical properties of a test structure of this type of device, incorporating an individual semiconductor photoanode and photocathode (with no redox catalysts) embedded into a candidate conducting polymer membrane, to form a single functional unit.

show abstract

Section: Discussionmentioning

confidence: 99%

Comparison between the electrical junction properties of H-terminated and methyl-terminated individual Si microwire/polymer assemblies for photoelectrochemical fuel production

Yahyaie

Ardo

Oliver

et al. 2012

Energy Environ. Sci.

View full text Add to dashboard Cite

show abstract

“…This technique has been used for characterizing various systems like e.g. Si nanowires [1,2,3], colloidal quantum dots [4], VO 2 nanobeams [5], carbon nanotubes [6,7,8,9,10,11,12,13,15] as well as 2D materials like graphene [16,17,18,19,20,21,22,23] and MoS 2 [24,25]. In such nanoscale systems, two mechanisms have been identified for the generation of photocurrent: i) photovoltaic processes where photo-excited carriers are separated by built-in electrical fields and ii) photothermal processes where thermoelectric forces drive carriers through light-induced thermal gradients.…”

Section: Introductionmentioning

confidence: 99%

Identifying signatures of photothermal current in a double-gated semiconducting nanotube

2014

View full text Add to dashboard Cite

).The remarkable electrical and optical properties of single-walled carbon nanotubes (SWNT) have allowed for engineering device prototypes showing great potential for applications such as photodectors and solar cells. However, any path towards industrial maturity requires a detailed understanding of the fundamental mechanisms governing the process of photocurrent generation. Here, we present scanning photocurrent microscopy measurements on a double-gated suspended semiconducting SWNT and show that both photovoltaic and photothermal mechanisms are relevant for the interpretation of the photocurrent. We find that the dominant or non-dominant character of one or the other processes depends on the doping profile, and that the magnitude of each contribution is strongly influenced by the series resistance from the band alignment with the metal contacts. These results provide new insight into the interpretation of features in scanning photocurrent microscopy and lay the foundation for the understanding of optoelectronic devices made from SWNTs. [6,7,8,9,10,11,12,13, 15] as well as 2D materials like graphene [16,17,18,19,20,21,22,23] and MoS 2 [24,25]. In such nanoscale systems, two mechanisms have been identified for the generation of photocurrent: i) photovoltaic processes where photo-excited carriers are separated by built-in electrical fields and ii) photothermal processes where thermoelectric forces drive carriers through light-induced thermal gradients.Single-walled carbon nanotubes (SWNT) are long, one dimensional conductors with a band structure ranging from quasimetallic (bandgap E g ∼ 30 meV) to semiconducting character (E g typically in the range of 0.1 to 1 eV) depending on chirality and diameter. These properties make SWNTs an ideal platform for exploring photocurrent generation with SPCM. In early single-walled nanotubes SPCM work the interpretation of photocurrent was mostly based on photovoltaic mechanisms [6,7,8,9,11].The importance of photothermal effects has been suggested in the context of measurements of bulk SWNT films [12,13,14] and very recently, SPCM work on graphene and individual metallic SWNTs has emphasized the importance of photothermal mechanisms in materials with no or small bandgaps [22,26].The question of the role of photothermal mechanisms in larger bandgap semiconducting nanotubes has been studied very recently in double-gated [26] and single-gated [27] suspended carbon nanotube devices.These two studies report contradictory results, leaving the understanding of fundamental mechanisms underlying photocurrent generation in semiconducting nanotubes unclear.Here we report on the study of a suspended semiconducting nanotube device where we show that both photovoltaic and photothermal mechanisms compete in the generation of photocurrent. In particular, we find that the dominant or non-dominant character of one or the other processes is a function of the doping profile and that the magnitude of each contribution is strongly influenced by the band alignment with the metal contacts throu...

show abstract

“…Using a separate substrate for the monolayer formation simplifies the overall surface doping process, does not require the deposition and removal of SiO 2 capping layer, allowing removal of the native oxide layer from the target substrate for enhanced dopant incorporation. Furthermore, intrinsic nanowires doped by MLCD process were shown to exhibit highly uniform longitudinal dopant distribution that is difficult to achieve by in-situ CVD nanowires synthesis 1,9 .…”

Section: Discussionmentioning

confidence: 99%

Monolayer Contact Doping of Silicon Surfaces and Nanowires Using Organophosphorus Compounds

Hazut

Agarwala

Subramani

et al. 2013

JoVE

View full text Add to dashboard Cite

Monolayer Contact Doping (MLCD) is a simple method for doping of surfaces and nanostructures 1 . MLCD results in the formation of highly controlled, ultra shallow and sharp doping profiles at the nanometer scale. In MLCD process the dopant source is a monolayer containing dopant atoms.In this article a detailed procedure for surface doping of silicon substrate as well as silicon nanowires is demonstrated. Phosphorus dopant source was formed using tetraethyl methylenediphosphonate monolayer on a silicon substrate. This monolayer containing substrate was brought to contact with a pristine intrinsic silicon target substrate and annealed while in contact. Sheet resistance of the target substrate was measured using 4 point probe. Intrinsic silicon nanowires were synthesized by chemical vapor deposition (CVD) process using a vapor-liquidsolid (VLS) mechanism; gold nanoparticles were used as catalyst for nanowire growth. The nanowires were suspended in ethanol by mild sonication. This suspension was used to dropcast the nanowires on silicon substrate with a silicon nitride dielectric top layer. These nanowires were doped with phosphorus in similar manner as used for the intrinsic silicon wafer. Standard photolithography process was used to fabricate metal electrodes for the formation of nanowire based field effect transistor (NW-FET). The electrical properties of a representative nanowire device were measured by a semiconductor device analyzer and a probe station. Video LinkThe video component of this article can be found at

show abstract

Nonuniform doping distribution along silicon nanowires measured by Kelvin probe force microscopy and scanning photocurrent microscopy

Cited by 87 publications

References 18 publications

Comparison between the electrical junction properties of H-terminated and methyl-terminated individual Si microwire/polymer assemblies for photoelectrochemical fuel production

Comparison between the electrical junction properties of H-terminated and methyl-terminated individual Si microwire/polymer assemblies for photoelectrochemical fuel production

Identifying signatures of photothermal current in a double-gated semiconducting nanotube

Monolayer Contact Doping of Silicon Surfaces and Nanowires Using Organophosphorus Compounds

Contact Info

Product

Resources

About