Direct Fabrication of Nanoscale Light Emitting Diode on Silicon Probe Tip for Scanning Microscopy

Kazunori Hoshino, Member, IEEE, Lynn J. Rozanski,
David A. Vanden Bout, and Xiaojing Zhang, Member, IEEE

JOURNAL OF MICROELECTROMECHANICAL SYSTEMS, VOL. 17, NO. 1, FEBRUARY 2008

Purpose

Near-field scanning optical microscopy (NSOM), combines scanning probe technology with optical microscopy. Conventionally, a fiber optic tip is assembled on the probe tip. This slows the fabrication process and requires an external light source. This purpose of this work is to integrate a nano-sized LED on the tip of the scanning probe.

Method

The fabrication can be divided into two parts: tip fabrication and LED fabrication.

Tip fabrication: started with a SoI wafer using the oxide as resist. An electrode was patterned on one side. The tip was subsequently etched to a tip.

LED fabrication: First the electrode part was doped, then trimmed with a focused ion beam (FIB) creating a 100nm gap. The probe was then charged in a solution of CdSe/ZnS core-shell nanoparticles of about 5nm in diameter. Electrostatic forces caused the nanoparticles to assemble and bridge the gap.

Results

The probe was successfully tested in a standard NSOM setup with the following observations.

- The electrode tip exhibited diode electrical behavior.

- A broad emission frequency was observed due to doping of the electrode in addition to the use of the ion beam for fabrication. (which can be mitigated by using an e-beam)

Nanosphere Lithography Using Thermal Evaporation of Gold

Nanosphere Lithography Using Thermal Evaporation of Gold

Proceedings of the 2006 International Conference on Nanoscience and Nanotechnology, ICONN
B.S. Flavel1, J.G. Shapter1,*, J.S. Quinton1
1School of Chemistry, Physics & Earth Sciences
Flinders University, Sturt Road, Bedford Park, Adelaide SA 5001

Purpose

The manufacture of metallic nanoparticle ararys have applications in biosensors, data storage, photonics, catalysis, and etching masks. This article shows how a large array of gold nanoparticles were formed on a substate.

Method

1. Mica substrate was treated with surfactant Triton X-100. This is to increase the hydrophilicity of mica.

2. Two drops of 500nm monodispersed polystyrene nanosphere suspensions were put on the mica forming a 2D hexagonal closed packed monolayer of polystyrene. A second layer, stacked on the first, was also made by adding more polysyrene suspension. In another trial, 1um polystyrene suspensions were used.

3. A layer of gold was deposited on the polystyrene by heating gold in a vacuum.

4. The polystyrene layer was removed by ultrasonication in ethanol.

Results

- When using the 500nm suspensions, gold nanoparticles of about 100nm were deposited in the voids between the polystyrene atoms in the hexagonal closed packed monolayer. Smaller particles were formed when the monolayers were stacked in a AB arrangement. The 1um suspensions gave 200nm sized nanoparticles for the single monolayer case.

- The thermal nature of the deposition process resulted in smaller voids due to annealing of the polystyrene layer.

Batch fabrication of carbon nanotubes at AFM probe tips and AFM imaging

Kazuhiko TAKAGAHARA, Yusuke TAKEI, Eiji IWASE, Kiyoshi MATSUMOTO, and Isao SHIMOYAMA
Graduate School of Information Science and Technology, The University of Tokyo, JAPAN

Purpose

Conventional AFM tips can be enhanced by attaching carbon nanotubes to their tips. Carbon nanotubes enhance tips’ toughness and horizonal resolution due to their strength and nanometer-scale diameters, respectively.

Method

Single wall carbon nanotubes were synthesized on an array of commercial silicon AFM tips using CVD. First, an oxidation layer was formed on the AFM tip. Second, the AFM tip was dipcoated in CNT-forming catalyst. Third, the array was put on a titanium jig where the AFM tips formed an electode with a counter silicon electrode. A high electric field was formed at the AFM tip (due to curvature). Then, argon gas plus ethanol were introduced to initate CNT growth.

Results

- Resonance Raman spectroscopy confirmed the formation of single-walled CNT of diameter ~1.2nm.

- Improved horizontal resolution was obeserved when passing the CNT-AFT tips over photoresist nanograting.

Thermal Conductivity of Polyethylene Chains Using Molecular Dynamics Simulations

Thermal Conductivity of Polyethylene Chains Using Molecular Dynamics Simulations

Asegun Henry and Gang Chen

Proceedings of 3rd Energy Nanotechnology International Conference
ENIC2008
August 10-14, 2008, Jacksonville, Florida USA

Purpose and Motivation

Polyethylene (and polymers in general) have low thermal conductivity. However, when mechanically stretched, polyethylene exhibits an order of magnitude increase in thermal conductivity. Since polyethylene is cheap, this motivates the study for its use in thermal applications.

The purpose of the study was to find the heat conductivity limit along a single chain of polyethylene.

Method

A modified molecular dynamics code, LAMMPS, was used to infer thermal conductivity. The polyethylene atoms were modeled as a chain with boundary conditions. The hydrogen and carbon atoms had their own degrees of freedom using the AIREBO potential.

The Green-Kubo relations were used to find thermal conductivity from the molecular trajectories.

Results

Infinite (theoretical) thermal conductivity was found for large systems. Faster divergence occurred with increased system size.

A finite thermal conductivity was calculated for small systems.

Conclusions

The resultant thermal conductivity figures arise from a physical aspect from the model (as opposed to numerical artifacts). In addition, the application of boundary conditions increases scattering of phonons; hence, smaller systems experienced slower divergence.

So, heat conduction in bulk polyethylene limited by disordered entanglement.

Notes:

LAMMPS: Large-scale Atomic/Molecular Massively Parallel Simulator developed by Sandia Labs.

AIREBO: Adaptive Intermolecular Reactive Empirical Bond Order potential is an empirical classical many-body potential.

Green-Kubo relations: give exact mathematical expression for transport coefficients in terms of integrals of time correlation functions.