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New Scanning Probe Microscopy methods and development of the next generation nanoscale imaging probes and instrumentation

Motivation

Devices, processes and objects with a nanometer size become increasingly important in science, technology and everyday life. It is envisaged that the mastering of nanoscale will help create novel instruments and processes that will improve economic performance and also help citizens. Already today the semiconductor technology is based on 250 nm wide structural features. In other fields it is envisaged that the single macromolecules can be handled and operated by ultrafine tools. Ultimate high density storage devices will be operated on length scalesapproaching the 10 nm size. There is a need to work on novel systems of near field optical excitation and detection. Experimental work must be accompanied by theoretical studies and should lead to a useful set of tools.

Objectives

Imaging of the test samples using both novel and conventional probes. Imaging the same or identical samples in different modes: shear-force AFM, SNOM (reflection and transmission), fluorescence imaging of biological samples using Quantum dots for labeling and different light collection mechanisms, development of SPM instrumentation. Recording of bits of information on ferroelectric samples, visualisation of the recorded information.

Our group has 15 years experience in scanning probe microscopy, including STM, AFM and SNOM. In 1996 we have constructed a versatile contact/force-modulation/noncontact AFM and demonstrated possibility to work on higher modes of cantilever to increase a resolution and in 2003 we have implemented an aperture-SNOM head in the illumination mode which can be operated in both transmission and reflection configurations. The photon counting module was developed and inserted in our SNOM equipment. In 2004 we developed and built the Bio-AFM with integrated flexures type XYZ positioning stage and combined with inverted Nicon-2000 optical microscope. Currently we are working on apertureless SNOM which uses AFM tips as scattering source of near field photons and possibilities to implement SERS methods into our SPM technique.We have investigated the AFM long range interaction forces between silicon tips and surfaces and we have experience on ferroelectric thin films and piezo-AFM.

Our group will contribute with investigations on:

- imaging of test samples by AFM, SNOM, shear-force AFM, STM.
- imaging and manipulation of biological samples, cells in liquids
- tip-surface interaction enhanced methods

We are working in collaboration with other research groups in Lithuania, Europe and US

Atomic force microscopy (AFM)

We have designed and built a research oriented atomic force microscope operating in intermittent contact mode and constant contact mode in air. Main features of our AFM are: piezostack actuated XY sample scanning stage ensuring high orthogonality, low drift and absence of cross-coupling; piezotube or piezostack actuated Z scanner; monolithic design of AFM basis and head for high anti-vibration stability; easy access to cantilevers via exchangeable cantilever tables; robust construction of cantilever vibration piezo for easy operation in liquids, including fast, long range ultrasonic motors coarse XY positioning stage for nanomanipulation. The Quesant Q-Scope 250 and NT-MDT Inc., microscopes are used for routine measurements.

Home-built AFM with sample nanomanipulation ......by ultrasonic motors

...............................Quesant Q-Scope 250

SPM instrumentation (AFM, STM, SNOM) are used for education of undergraduate and postgraduate students from Kaunas university of Technology, Vilnius University, Vytautas Magnus University, Vilnius Gediminas University, Lithuanian University of Agriculture.

Biological AFM

Home built Bio_AFM with possibility to position the cantilever tip over the single cell in liquid using inverted optical microscope.
Students Marija Jankunec ir Ieva Kairyte from Vilnius Gedimino Technical University working on bachelor degree thesis investigating Saccharomyces cerevisiae virus by Atomic Force Microscopy

 

Manualy controled nanopositioning XY stage combined with NT-MDT Inc., AFM head based on XYZ -piezotube scanner.

AFM head we designed to control the position of the cantilever tip over the single cell with possibility to get an optical image in inverted or reflection optical modes.The nanopositioning can be controled manualy by precision positioning of the head by micro-screws couplings and fine positioning by flexures based XYZ (25x25x6) nanopositioning stage

Scanning Tunneling (STM) and Electrochemical Microscopy

NT_MDT Inc., STM microscope with 1-5 nA measurement head.

 

 

Scanning Near Field Optical Microscopy

Semicomductor physics and life sciences have an urgent need for optical imaging tools that resolve features with size of 1 to10 nm. Optical techniques have extremely high energy (spectral) and temporal resolution. They are one of the workhorses to analyse materials and samples: our technology standard is based to a great extent on the availability of optical microscopes.
One of the possibilities to extend the resolution of optical microscopes is to use point by point an ultra small light source or detector. Near Field Optical Microscopes (SNOM) based on this principle have been operated with super resolution. Although this tool is routinely used in laboratories and although many types of technologically important experiments have been carried out, it is generally recognised that additional technological advances and conceptual improvements are needed. The Surface Enhanced Raman Spectroscopy methods in combination with SNOM technique can improve the optical resolution up to nanometers and to get the information about the chemical composition of the nanostructures, for example by nano-Raman scattering.ObjectivesOur objectives within this research are the developmentof of technique for the cells fluorescense imaging by transmision or reflection aperture tip SNOM, investigation of possibilities to use Q-dots for labeling. We use a shear-force quartz tunning-fork sensor for the feed-back control and aperture tips for the light collection, including home made photon counting system.
Our research includes characterization of shear-force effects both on amplitude damping, phase shift and resonance frequency shift being performed and the possibility to apply SNOM for the biological samples investigation. Improved resolution and sensitivity will be provided by a surface enhanced apertureless SNOM. We developed a technology of gold nanoparticle synthesis and are working on application of SERS for SNOM.

SNOM with photon counting system:

C - NT-MDT Inc., SNOM head with shear-force controled feedback and piezotube (100x100x5) microns XYZ scanner.

B - XYZ (25x25x5) micron flexure pozitioning stage for laser-tip focusing.

A - photon counting PMT.