Individual Nano-objects Research Articles

Interconnection of specific nano-objects by electron beam lithography — A controllable method

We report a widely applicable and highly controlled approach, based on electron beam lithography (EBL), to interconnect single nano-objects, previously immobilized onto solid surfaces, and to investigate the transport properties at the level of single nanostructures. In particular, a three-step EBL-procedure was used for this purpose by patterning two planar contacts on the sides of an individual nano-object. To demonstrate this approach, we use two different kinds of active elements: a semiconductor nanocrystal (tetrapod) and a thin triangular gold nanoprism (NT).

Nanomanipulation and characterisation of individual nano-objects inside a SEM

This paper describes the use of nanomanipulation for deforming, picking up and positioning nano-objects in situ in a field emission scanning electron microscope using an in-house built manipulator. Our experiments demonstrate that physical manipulation can be used in a wide range of different experiments and systems. The scope of possibilities is quite large, from mounting nanodevices to fabricating AFM tips based on CNTs in addition to measuring mechanical and electrical properties of individual nanosystems. Nanomanipulation has a large application potential in physics, chemistry, biology and engineering, rendering possible the idealised bottom-up approach to nanotechnology.

Magneto-optics of layers of semiconductor quantum dots and nano-rings

We have studied the collective magneto-optical response of layers of semiconductor quantum dots and nano-rings. Expressions for both the polarizability of the individual nano-objects have been used to determine the magneto-optical response on square two-dimensional lattices on those nano-objects as a function on frequency, magnetic field and angle of incidence. The magnetic field dependence of the response for layers of rings gives rise to the Aharonov-Bohm type oscillatory behavior in the reflectance and absorbance that can be measurable. Layers of dots do not display any remarkable magnetic field dependence.

Highly-regulated nanocoatings of polymer films on carbon nanofibers using ultrasonic irradiation

It was demonstrated that nanoprecise coatings of uniform and densely packed polymer layers on nanomaterials and uniform polymer coatings on individual nano-objects are formed using ultrasonic effects.

Can scanning tunnelling spectroscopy measure the density of states of semiconductor quantum dots?

Molecules, supramolecular structures and semiconductor nanocrystals are increasingly used as the active components in prototype opto-electrical devices with miniaturized dimensions and novel functions. Therefore, there is a strong need to measure the electronic structure of such single, individual nano-objects. Here, we explore the potential of scanning tunnelling spectroscopy to obtain quantitative information on the energy levels and Coulomb interactions of semiconductor quantum dots. We discuss the conditions under which shell-tunnelling, shell-filling and bipolar spectroscopy can be performed, and illustrate this with spectra acquired on individual CdSe and PbSe quantum dots. We conclude that quantitative information on the energy levels and Coulomb interactions can be obtained if the physics of the tip/quantum dot/substrate double-barrier tunnel junction is well understood.

Interconnecting single nano-objects on surfaces for transport experiments

The authors report a highly controlled approach, based on electron-beam lithography, to interconnect individual nano-objects for transport experiments. The process is based on a three-step procedure, consisting of fabrication of four alignment markers, localization of the nano-object after its immobilization onto functionalized surfaces, and interconnection of the single nanostructure by patterning two nanoelectrodes on its sides. The approach is highly reproducible and widely applicable and allows an alignment accuracy of 15–20nm. Here they demonstrate the reliability of such technique by using a thin triangular gold nanoprism as the active element and show the I-V characteristics of the single nanostructure.

"Electron Tweezers" as a Tool for In-situ Manipulation and Processing of Individual Metal Nanoparticles in a Two-Phase Partially Molten Alloy

Vladimir P. Oleshko and James M. Howe University of Virginia, Department of Materials Science & Engineering, Charlottesville, VA 22904 Understanding physical principles for controlling the dynamic behavior of nanoparticles in inhomogeneous gas (liquid) – solid systems is becoming increasingly important for nanoscience and technology. Nondestructive trapping of micron- and nano-sized dielectric and metal particles in a liquid using a laser beam, which is refracted by the particle and transfers momentum to it, is known as a single-beam gradient force optical trap, or optical tweezers [1]. Recent experiments utilizing partially molten submicron-sized Al-Si alloy spheres and a focused electron beams in a medium-voltage TEM [2] and theoretical calculations of linear and angular momentum transfer from an electron beam to small particles [3] indicate that optical trapping of particles using electron beams may occur. Such thermally assisted “electron tweezers” potentially can be utilized for manipulation and processing of individual nanoobjects and fabrication of assembled nanodevices with up to atomic level sensitivity and lateral resolution provided by modern electron optical systems. In this work, we demonstrate electron-beam trapping of solid nanoparticles inside opaque submicron-sized Al-Si alloy spheres using energy filtering TEM (EFTEM) and parallel electron energy-loss spectroscopy (PEELS). Thermally assisted motion of crystalline Al nanospheres confined within the partially molten Al-Si particles was initiated by the electron beam, which was used to control and to observe the trapping in real-time by plasmon spectroscopic imaging (Fig. 1). Such approaches enable

Development of x-ray nanodiffraction instrumentation for studies of individualnano-objects

X-ray nanodiffraction was developed to study individual crystalline nano-objects at theAdvanced Photon Source (APS). This technique allows nondestructive structuralcharacterization of individual nano-objects with the advantages of high structuralsensitivity and high penetration. Using the extremely high brightness of a third-generationsynchrotron radiation source and hard x-ray phase zone-plate optics, we have focused hardx-rays to a microbeam of less than 200 nm during routine operation so that significantdiffraction can be measured from a single tin oxide nanowire (cross section down to24 nm × 10 nm). In this paper, we will describe the experimental technique in detail and present theresults of a structural study of a few tin oxide nanowires.

C14 An X-ray Nanodiffraction Technique for Individual Crystalline Nanoobjects

C14 An X-ray Nanodiffraction Technique for Individual Crystalline Nanoobjects

SINGLE-MOLECULE OPTICS

We review recent developments in single-molecule spectroscopy and microscopy. New optical methods provide access to the absorption, emission, or excitation spectra of single nano-objects and can determine either the positions of these objects with subwavelength accuracy or the full three-dimensional orientation of their transition dipole moments. Recent work aims at using single molecules as nanoparts or nanoelements in a variety of molecular-scale devices, from triggered sources of single photons to single-molecular switches. A prominent new direction explores the various interactions between molecules within individual multichromophoric systems obtained by chemical synthesis. These systems are the models for natural self-assembled systems such as the light-harvesting proteins of bacteria and green plants, which are currently studied on a single-molecule basis. Another important class of multichromophoric systems are conjugated polymers. The combination of microscopy with time- and frequency-resolved spectroscopy is opening a wide field of new and exciting applications to individual nano-objects.

Nanodevices for correlated electrical transport and structural investigation of individual carbon nanotubes

We report a new approach to the correlation of the structural properties and the transport properties of carbon nanotubes. Through an original combination of UV lithography, custom-made photosensitive sol–gel resist and deep reactive ion etching (RIE), we have successfully integrated membrane technology and nanodevice fabrication for the electrical connection of individual carbon nanotubes. After single wall nanotube (SWNT) deposition by molecular combing and contacting using high resolution electron beam lithography, we obtain a device that allows both the investigation of the nanotubes and the contact regions by transmission electron microscopy (TEM) and the measurement of the electronic transport properties of the same individual nano-object. The whole fabrication process is detailed and the demonstration that the micro membranes are suitable for both TEM inspection and nanoelectrode fabrication is given.

Measuring chemical and electronic properties of individual nano-objects

Measuring chemical and electronic properties of individual nano-objects