Our goal is to develop the metrology to enable a materials genomic approach to the discovery and optimization of complex electronic and electromagnetic materials. To advance these goals we apply measurement-based approaches to rapidly determine the electromagnetic, thermal, and mechanical properties of complex thin-film materials, interfaces, and microstructures. Reliable, quantitative data for the relevant material parameters are critical to achieve accurate modeling of device performance for microelectronic circuits and applications. Our approach relies heavily on a generalized description of the material parameters (such as permittivity, heat capacity, elasticity) that explicitly includes nonlinear, inhomogeneous, and anisotropic behavior, and which can also incorporate non-equilibrium and quantum effects.
We approach this multidimensional characterization problem by developing measurement-based techniques to rapidly quantify all of the relevant properties of thin-film materials, interfaces, and microelectronic structures. We make extensive use of finite-element simulations, as well as linear and non-linear circuit models, in order to determine consistent material properties from measurements of ensembles of planar or microelectronic devices, and supplement device-based characterization with spatially-resolved measurements where possible. These measurement-based material descriptions can then be compared and combined with results of computational approaches to provide more complete models of complex systems, which are then used in the subsequent intelligent design and optimization of electronic materials, devices, and systems, and as a basis for new materials discovery.
Our measurement-based approach makes use of standardized, microfabricated test structures, such as planar transmission lines and simple lumped-element components. We then apply wafer-probe-based measurements as well as scanned-probe approaches to quantify different material parameters for a given material orientation. We have developed a comprehensive suite of measurements to access the multiple different material parameters most relevant for modeling device performance:
- Quantitative measurement of the broadband permittivity and permeability over the range of frequencies of interest for most electronic applications (several Hz to > 500 GHz);
- Measurement of spatially-resolved electromagnetic properties down to nanometer length scales;
- Electromagnetic measurements to quantify effects of temperature and strain on material properties;
- Determination of higher-order material coefficients from nonlinear measurements;
- Electromagnetic measurements in the presence of electric- and magnetic-field biases, to determine cross-couplings of different phenomena (magnetoelectric coefficient, piezoelectric coefficient, etc.);
- Electronic measurement of thermal properties.
We also possess the metrology expertise to carry out electromagnetic material characterization with atomic-scale spatial resolution. As the electronics, semiconductor, and storage technology industries scale down to features and components consisting of only a few atoms, this metrology is becoming more and more critical. At this scale, individual dopants and and defects critically influence behavior and modeling of electronic materials. In addition to the characterization of the atomic-scale systems themselves, we are studying approaches to interconnects and other signal-control strategies that may cross multiple length scales.
Additional Technical Details:
We rely on collaborations with universities, industry, and government agencies to obtain physical samples of different material systems and microstructures, and work closely with these collaborators to improve material growth and fabrication processes by quantifying relevant electromagnetic material properties. Examples of material systems of interest include
- Electronically tunable materials, e.g., ferroelectrics such as barium strontium titanate;
- Magneto-electric materials, such as bismuth ferrite;
- Electro-acoustic materials, e.g., bulk acoustic wave (BAW) resonators incorporating aluminum nitride;
- Low-dimensional systems, e.g. topological insulators, graphene, nanotubes and nanowires;
- Highly correlated electron materials, e.g. superconductors, such as yttrium barium copper oxide;
- Other technologically important materials, such as transparent conducting oxides, thermoelectrics, electrocaloric materials.
- Individual atomic-scale dopants and defects
- Interconnects that bridge multiple length scales
We also actively seek collaborations with theoretical and computational material scientists in order to quantitatively compare experimental descriptions of material parameters with ab-initio calculations and results of other computational approaches. Such collaborations not only provide important experimental verification for computational approaches to material parameter determinations, but also help to guide and focus experimental investigations.
Dielectrics and Ferroelectrics
Booth, J. C.; Orloff, N. D.; Cagnon, J.; Lu, J. & Stemmer, S.,"Temperature-dependent dielectric relaxation in bismuth zinc niobate thin films," Applied Physics Letters 97, 022902 (2010).
Orloff, N. D.; Tian, W.; Fennie, C. J.; Lee, C. H.; Gu, D.; Mateu, J.; Xi, X. X.; Rabe, K. M.; Schlom, D. G.; Takeuchi, I. & Booth, J. C., "Broadband dielectric spectroscopy of Ruddlesden-Popper Srn+1TinO3n+1 (n=1,2,3) thin films," Applied Physics Letters 94, 042908 (2009).
Booth, J. C.; Orloff, N. D.; Mateu, J. & Takeuchi, I., "Methods of characterization of broadband dielectric properties, challenges in device fabrication and measurement," in Ferroelectric Films at Microwave Frequencies, edited by Jackson, T.; Suherman, P. & Bao, P., (Research Signpost, Kerala, 2010).
Bulk Acoustic Wave Devices
Collado, C.; Rocas, E.; Padilla, A.; Mateu, J.; O'Callaghan, J.; Orloff, N.; Booth, J.; Iborra, E. & Aigner, R., "First-Order Elastic Nonlinearities of Bulk Acoustic Wave Resonators,"IEEE Transactions onMicrowave Theory and Techniques, 59, 1206-1213 (2011).
Rocas, E.; Collado, C.; Booth, J. C.; Iborra, E. & Aigner, R., "Unified Model for Bulk Acoustic Wave Resonators Nonlinear Effects," Proceedings of the IEEE International Ultrasonics Symposium (IUS 2009), 2009.
Orloff, N.; Mateu, J.; Murakami, M.; Takeuchi, I. & Booth, J. C., "Broadband Characterization of Multilayer Dielectric Thin-Films," 2007 IEEE/MTT-S International Microwave Symposium Digest, 1177-1180 (2007).
Nanoscale Characterization of Semiconductors and Photovoltaics
Rocas, E.; Collado, C.; Mateu, J.; Orloff, N.; O'Callaghan, J. M. & Booth, J. C., "A Large-Signal Model of Ferroelectric Thin-Film Transmission Lines," IEEE Transactions on Microwave Theory and Techniques 59, 3059-3067 (2011).
Rocas, E.; Collado, C.; Orloff, N.; Mateu, J.; Padilla, A.; O'Callaghan, J. & Booth, J., "Passive Intermodulation Due to Self-Heating in Printed Transmission Lines,"IEEE Transactions on Microwave Theory and Technique 59, 311-322 (2011).
Booth, J. C.; Orloff, N. D. & Mateu, J., "Measurement of the Microwave Nonlinear Response of Combined Ferroelectric-Superconductor Transmission Lines," IEEE Transactions on Applied Superconductivity 19, 940-943 (2009).
Mateu, J.; Collado, C.; Orloff, N.; Booth, J. C.; Rocas, E.; Padilla, A. & O'Callaghan, J. M., "Third-Order Intermodulation Distortion and Harmonic Generation in Mismatched Weakly Nonlinear Transmission Lines,"IEEE Transactions on Microwave Theory and Techniques 57, 10-18 (2009).
Nanowires and Nanotubes
- J.C. Weber, J.B. Schlager, N.A. Sanford, A. Imtiaz, T.M. Wallis, L.M. Mansfield, K.J. Coakley, K. Bertness, P. Kabos, and V.M. Bright, "A near-field scanning microwave microscope for characterization of inhomogeneous photovoltaics," Review Scientific Instrum. 83, 083702 (2012).
- A. Imtiaz, T.M. Wallis, S.-H. Lim, H. Tanabakuchi, H.-P. Huber, A. Hornung, P. Hinterdorfer, J. Smoliner, F. Kienberger, and P. Kabos, "Frequency-selective contrast on variably doped p-type silicon with a scanning microwave microscope," J. Appl. Phys. 111, 093727 (2012).
- P. Huber, M. Moertelmaier, T.M. Wallis, C.J. Chiang, M. Hochleitner, A. Imtiaz, Y.J. Oh, K. Schilicher, M. Dieudonne, J. Smoliner, P. Hinterdorfer, S.J. Rosner, H. Tanabakuchi, P. Kabos, and F. Lienberger, "Calibrated nanoscale capacitance measurements using a scanning microwave microscope," Rev. Scientific Instrum. 81, 113701 (2010).
- T.M. Wallis, D. Gu, A. Imtiaz, C.S. Smith, C.-J. Chiang, P. Kabos, P.T. Blanchard, N.A. Sanford, and K.A. Bertness, "Electrical characterization of photoconductive GaN nanowire devices from 50 MHz to 33 GHz," IEEE Trans. Nanotechnology 10, 832 (2011).
- K.C. Kim, T.M. Wallis, P. Rice, C.-J. Chiang, A. Imtiaz, P. Kabos, and D.S. Filipovic, "A framework for broadband characterization of individual nanowires," IEEE Microwave Wireless Component Lett. 20, 178 (2010).
Diagram showing the electro-thermo-mechanical relations in a crystal, where T, S, E, D, θ and σ are stress, strain, electric field, electric displacement, temperature and entropy respectively.
October 1, 2012
Lead Organizational Unit:
James C. Booth
T. Mitch Wallis
Related Programs and Projects: