Teodor Gotszalk

Piezoresistive sensors for scanning probe microscopy

In this article we summarize the efforts devoted to the realization of our ideas of the development of piezoresistive sensor family used in scanning probe microscopy. All the sensors described here are fabricated based on advanced silicon micromachining and standard CMOS processing. The fabrication scenario presented in this article allows for the production of different sensors with the same tip deflection piezoresistive detection scheme. In this way we designed and fabricated, as a basic sensor, piezoresistive cantilever for atomic force microscopy, which enables surface topography measurements with a resolution of 0.1 nm. Next, by introducing a conductive tip isolated from the beam we obtained a microprobe for scanning capacitance microscopy and scanning tunneling microscopy. With this microprobe we measured capacitance between the microtip and the surface in the range of 10(-22) F. Furthermore, a modification of the piezoresistors placement, based on the finite element method (FEM) simulation permits fabrication of the multipurpose sensor for lateral force microscopy, which enables measurements of friction forces with a resolution of 1 nN. Finally, using the same basic device idea and only slightly modified process sequence we manufactured femtocalorimeter for the detection of heat energy in the range of 50 pJ.

Micromachined piezoresistive cantilever array with integrated resistive microheater for calorimetry and mass detection

We describe a microcantilever calorimeter consisting of an array of ten cantilevers. Each single cantilever is capable of detecting heat energy with the resolution of 50 nW Hz(−0.5). The device is based on a Si microcantilever coated with a 1 μm thick layer of SiO2 deposited with a 700 nm thick layer of aluminum which forms a resistive microheater. Heat fluxes are monitored by detecting the cantilever deflection (bending) due to the bimaterial structure of the cantilever (dissimilar thermal expansion properties of SiO2 and Al). The resistive microheater serves for calibration of the heat flux and for temperature sensing. In our design a piezoresistive Wheatstone bridge detector is applied for measurements of the cantilever beam deflection. The cantilever displacement detection system enables investigations in ultrahigh vacuum and low temperature conditions. The microcantilevers are manufactured in a one-dimensional array having ten individual microcantilevers which is the first step in the fabrication of ...

Thermal nano-probe

The novel thermal probe presented here is based on the changes of the electrical resistivity of a nanometer-sized filament with temperature. The filament is integrated into an atomic force scanning probe piezoresistive type cantilever. Using a focused ion beam technique, the front end of the Al meander is cut through, forming an approximately 1-μm wide gap. Employing an electron beam deposition technique a sub-100 nm diameter Pt filament is deposited across the gap. The filament consists of an approximately 2-μm high loop with an additional spike deposited at the apex of the loop to improve spatial resolution. The new probe is an example on how a combination of CMOS technology, bulk and surface micromachining, focused ion beam technology and electron beam-induced deposition can be used to successfully fabricate unique nanoprobes. A spatial resolution of the order of 20 nm and a thermal resolution of 10−3 K is obtained.

Evaluation and fabrication of AFM array for ESA-Midas/Rosetta space mission

The MIDAS (Micro-Imaging Dust Analysis System) experiment is dedicated to the micro-textural and statistical analysis of cometary dust particles. The instrument is based on the technique of atomic force microscopy. The comparative simplicity and robustness of the technique lends itself to advanced space applications. The instrument is considered as essential for this mission since, for the first time, it has the capability of three-dimensional imaging of interplanetary and pristine cometary particles in the manometer to micrometer range. In this paper we describe our effort to evaluate and fabricate the AFM arrays for the ESA-Midas/Rosetta space mission.

Application of a Scanning Thermal Nano-Probe for Thermal Imaging of High Frequency Active devices

The first application of a new thermal nano-probe based on the changes of electrical resistivity of a nanometer-sized filament with temperature has been presented for the thermal imaging of microwave power active devices. The integration of the filament the fabrication process of the novel thermal probe with a spatial resolution better than 80 nm and a thermal resolution of the order of 10-3 K have already been presented in reference [J. Microelectron. Eng. 57–58 (2001) 737]. To demonstrate the capability of the novel thermal nano-probe the measurements have been successfully performed on a 30 fingers GaAs metal–semiconductor field-effect transistor (GaAs-MESFET) with a maximum power dissipation of 2.5 W. The bias circuit has been designed to suppress the undesired microwave oscillations in the transistor. In this case the power dissipation is equal to the dc power input. The near-field measurements using the nano-probe are compared with infrared measurement and three-dimensional finite element static thermal simulations. The good agreement between simulations and measurements confirms the high capability of the nono-probe for these applications.

P2.1.20 Single-beam multi-cantilever optical measurement head for cantilever array-based biosensors

Here we present a homemade system for highly sensitive measurements of cantilever sensor arrays. Two unique techniques developed by our group are utilized. Firstly, the expanded beam deflection (EBD) method that allows truly simultaneous measurements of multiple cantilevers with a simple optical apparatus consisting of a single and stationary laser beam, while providing the same sensitivity as the original optical beam deflection (OBD) method. Secondly, the real-time Brownian noise extraction technique allows combined static-dynamic mode operation in gaseous or liquid environment with no need for external excitation of vibrations. Thus constructed measurement system allows highly sensitive simultaneous measurement of bending as well as flexural and torsional vibrations of up to 8 cantilevers.