STM/STS measurement

Almost all the characterizations performed by us until now are ensemble characterizations (i.e. probing many nanostructures simultaneously). HRTEM and HRS EM do probe the structure (and elemental composition) of individual nanostructures, but they do not correlate this structure with a specific property. STM and STS measurements are real single-object measurements that reveal the size, shape, and surface atomic structure, as well as the electronic density of states (deduced the I-V characteristics). The STM/STS measurements offer a way to correlate the electronic properties of SiNWs with the nanostructure size. 

One advantage of STM/STS measurements is, that the individual duster can be imaged and analyzed spectroscopically in one single experiment, which ensures that reliable data are acquired from individual dusters. 

Surface-dependent tunneling spectra have been observed by Murakami and Aoki (1995). They performed low-temperature STM/STS measurements on a cleaved surface of Bi2212, and found three terraces eventually exposed by in situ cleavage. Here, as shown in fig. 13, the lowest and highest terraces had a one-step difference in height, and a square... 

Y. Niimi, T. Matsui, H. Kambara, H. Fukuyama, STM/STS measurements of two-dimensional electronic states trapped around surface defects in magnetic fields. Physica E 34(1-2), 100-103 (2006)... 

The first report of current-voltage (I-V) measurements by Zhang and Lieber[I0] suggested a gap in the density of states below about 200 MeV and semiconducting behavior in the smallest of their nanotubes (6 nm diameter). The study that provides the most detailed test of the theory for the electronic properties of the ID carbon nanotubes, thus far, is the combined STM/STS study by Oik and Heremans[l 1], even though it is still preliminary. In this study, more than nine... 

Yu et al. prepared 48, bound to an Au(lll) surface by a thiol on the biphenyl end, then deprotected on the bipyrimidine end to expose a thiol to bind an Au nanoparticle. Rectification was measured by scanning tunneling spectroscopy (STS), and it could be reversed by the addition of acid, which protonated the pyrimidine rings, converting them from donor to acceptor [121]. Yu s group has also inverted the attachment of a rectifier, as shown with 49 and 50, and confirmed that the rectification direction reversed [122]. This was recently verified by STM-BJ measurements [123]. 

In order to gain further insight into the growth and characterization of the deposited polymer film we acquired in situ STM and STS measurements. 

STM and STS measurements have been also performed on B-doped and undoped SiNWS [45] produced by OAG [23, 80]. The as-grown sample consisted primarily of SiNWs and nanoparticle chains coated with an oxide sheath. Samples for STM and STS measurements were prepared by dispersing the SiNWs into a suspension, which was then spin-coated onto highly oriented pyrolytic graphite (HOPG) substrates. The presence of nanoparticle chains and nanowires in the B-doped SiNWs sample was observed. Clear and regular nanoscale domains were observed on the SiNW surface, which were attributed to B-induced surface recon-... 

The combined STM and STS measurements revealed no changes of the BPn adlayer structures if the bias potential sweep was restricted to values... 

The abihty to measure and to control charge transport across nanometer-scale metal-molecule-metal junctions represents a key step toward the realization of molecular-based electronics [190-192]. Various experimental approaches have been employed to study molecular junctions in two- and three-terminal configurations. These include scanning probe microscopies (STM, STS, CP-AFM) [193-208], crossed-wire junctions [209], mechanical [210-215] and electromigration [216,217] break junctions, nanopores [218] and mercury drop electrodes [219]. Approaches in condensed media, and in par-... 

At a surface, not only can the atomic structure differ from the bulk, but electronic energy levels are present that do not exist in the bulk band structure. These are referred to as surface states . If the states are occupied, they can easily be measured with photoelectron spectroscopy (described in section A 1.7.5.1 and section Bl.25.2). If the states are unoccupied, a teclmique such as inverse photoemission or x-ray absorption is required [22, 23]. Also, note that STM has been used to measure surface states by monitoring the tunnelling current as a fiinction of the bias voltage [24] (see section BT20). This is sometimes called scamiing tuimelling spectroscopy (STS). 

Scanning tunneling spectroscopy (STS) can, in principle, probe the electronic density of states of a singlewall nanotube, or the outermost cylinder of a multi-wall tubule, or of a bundle of tubules. With this technique, it is further possible to carry out both STS and scanning tunneling microscopy (STM) measurements at the same location on the same tubule and, therefore, to measure the tubule diameter concurrently with the STS spectrum. No reports have yet been made of a determination of the chiral angle of a tubule with the STM technique. Several groups have, thus far, attempted STS studies of individual tubules. 

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