Mark R. Abel

Bio: Mark R. Abel is an academic researcher from Georgia Institute of Technology. The author has contributed to research in topics: Cantilever & Raman spectroscopy. The author has an hindex of 5, co-authored 7 publications receiving 198 citations.

Thermal conduction from microcantilever heaters in partial vacuum

Abstract: This paper reports the thermal and electrical characteristics of a heated microcantilever in air and helium over a wide range of pressures. The cantilever heater size modulates thermal conductance between the cantilever and its gaseous surroundings; and the Knudsen number, Kn characterizes this thermal conductance. When Kn 1, thermal transport from the cantilever heater remains constant. This measurement of thermal conductance around Kn=1 could aid the design and analysis of Pirani sensors and other microscale thermal sensors and actuators.

Thermal Metrology of Silicon Microstructures Using Raman Spectroscopy

Abstract: Thermal metrology of an electrically active silicon heated atomic force microscope cantilever and doped polysilicon microbeams was performed using Raman spectroscopy. The temperature dependence of the Stokes Raman peak location and the Stokes to anti-Stokes intensity ratio calibrated the measurements, and it was possible to assess both temperature and thermal stress behavior with resolution near 1mum. The devices can exceed 400degC with the required power depending upon thermal boundary conditions. Comparing the Stokes shift method to the intensity ratio technique, non-negligible errors in devices with mechanically fixed boundary conditions compared to freely standing structures arise due to thermally induced stress. Experimental values were compared with a finite element model, and were within 9% of the thermal response and 5% of the electrical response across the entire range measured

Raman Thermometry of Polysilicon Microelectro-mechanical Systems in the Presence of an Evolving Stress

Abstract: In this work, the use of Raman Stokes peak location and linewidth broadening methods were evaluated for thermometry applications of polysilicon microheaters subjected to evolving thermal stresses. Calibrations were performed using the temperature dependence of each spectral characteristic separately, and the uncertainty of each method quantified. It was determined that the Stokes linewidth was independent of stress variation allowing for temperature determination, irrespective of stress state. However, the linewidth method is subject to greater uncertainty than the Stokes shift determination. The uncertainties for each method are observed to decrease with decreasing temperature and increasing integration times. The techniques were applied to mechanically constrained electrically active polysilicon microheaters. Results revealed temperatures in excess of 500°C could be achieved in these devices. Using the peak location method resulted in an underprediction of temperature due to the development of a relative compressive thermal stress with increasing power dissipation.

Thermal metrology of silicon microstructures using Raman spectroscopy

Abstract: The effects of temperature and stress on the Raman shift in single crystal silicon and polycrystalline silicon films were calibrated. Polysilicon films were grown by LPCVD using a range of temperatures to produce amorphous and crystalline materials followed by doping and annealing. The dependencies of the linear coefficients were related to the polysilicon microstructure using AFM surface scans to determine any possible links. Finally, the technique was utilized in measuring the temperature distribution in a thermal MEMS cantilever device with micron spatial resolution.

Thermometry of Polycrystalline Silicon Structures Using Raman Spectroscopy

Abstract: Raman spectroscopy was investigated as a method for the temperature and stress measurement in thermal MEMS devices. Calibrations of the Stokes Raman shift and the Stokes to anti-Stokes intensity ratio for doped samples were performed in order to calculate the temperature on simple polysilicon structures. Straight and serpentine micro-heaters of various sizes were fabricated from 2 micron doped polysilicon films on thick sacrificial oxide layers. Operating temperatures were measured at a range of input powers for devices attached to the oxide layer as well as released structures. Measurements show that all devices can exceed 400°C with the released devices requiring much less power, as expected. Temperature measurements using the Stokes shift method were compared to the conventional intensity ratio method in order to deduce the effects of thermal stresses on the temperature measurements. Using this method, it was found that thermal stresses could be qualitatively determined simultaneously with temperature in silicon MEMS devices. The effects of stress, however, results in less than a 10% difference in temperature over all of the input powers tested in this study.Copyright © 2005 by ASME

Electrical, Thermal, and Mechanical Characterization of Silicon Microcantilever Heaters

Abstract: Silicon atomic force microscope (AFM) cantilevers having integrated solid-state heaters were originally developed for application to data storage, but have since been applied to metrology, thermophysical property measurements, and nanoscale manufacturing. These applications beyond data storage have strict requirements for mechanical characterization and precise temperature calibration of the cantilever. This paper describes detailed mechanical, electrical, and thermal characterization and calibration of AFM cantilevers having integrated solid-state heaters. Analysis of the cantilever response to electrical excitation in both time and frequency domains aids in resolving heat transfer mechanisms in the cantilever. Raman spectroscopy provides local temperature measurement along the cantilever with resolution near 1 mum and 5degC and also provides local surface stress measurements. Observation of the cantilever mechanical thermal noise spectrum at room temperature and while heated provides insight into cantilever mechanical behavior and compares well with finite-element analysis. The characterization and calibration methodology reported here expands the use of heated AFM cantilevers, particularly the uses for nanomanufacturing and sensing

Scanning thermal microscopy: A review

Abstract: Fundamental research and continued miniaturization of materials, components and systems have raised the need for the development of thermal-investigation methods enabling ultra-local measurements of surface temperature and thermo-physical properties in many areas of science and applicative fields. Scanning thermal microscopy (SThM) is a promising technique for nanometer-scale thermal measurements, imaging, and study of thermal transport phenomena. This review focuses on fundamentals and applications of SThM methods. It inventories the main scanning probe microscopy-based techniques developed for thermal imaging with nanoscale spatial resolution. It describes the approaches currently used to calibrate the SThM probes in thermometry and for thermal conductivity measurement. In many cases, the link between the nominal measured signal and the investigated parameter is not straightforward due to the complexity of the micro/nanoscale interaction between the probe and the sample. Special attention is given to this interaction that conditions the tip–sample interface temperature. Examples of applications of SThM are presented, which include the characterization of operating devices, the measurements of the effective thermal conductivity of nanomaterials and local phase transition temperatures. Finally, future challenges and opportunities for SThM are discussed.

Invited Article: Simultaneous mapping of temperature and stress in microdevices using micro-Raman spectroscopy.

Abstract: Analysis of the Raman Stokes peak position and its shift has been frequently used to estimate either temperature or stress in microelectronics and microelectromechanical system devices. However, if both fields are evolving simultaneously, the Stokes shift represents a convolution of these effects, making it difficult to measure either quantity accurately. By using the relative independence of the Stokes linewidth to applied stress, it is possible to deconvolve the signal into an estimation of both temperature and stress. Using this property, a method is presented whereby the temperature and stress were simultaneously measured in doped polysilicon microheaters. A data collection and analysis method was developed to reduce the uncertainty in the measured stresses resulting in an accuracy of +/-40 MPa for an average applied stress of -325 MPa and temperature of 520 degrees C. Measurement results were compared to three-dimensional finite-element analysis of the microheaters and were shown to be in excellent agreement. This analysis shows that Raman spectroscopy has the potential to measure both evolving temperature and stress fields in devices using a single optical measurement.

for Sandia National Laboratories

Abstract: Sandia National Laboratories is the nation's premier science and engineering lab for national security and technology innovation. We are a world‐class team of scientists, engineers, technologists, postdocs, and visiting researchers all focused on cutting‐edge technology, ranging from homeland defense, global security, biotechnology, and environmental preservation to energy and combustion research, computer security, and nuclear defense.