Donald B. Novotny

Application of the three omega thermal conductivity measurement method to a film on a substrate of finite thickness

The three omega thermal conductivity measurement method is analyzed for the case of one or more thin films on a substrate of finite thickness. The analysis is used to obtain the thermal conductivities of SiO2 films on Si substrates and of a chemical vapor deposition (CVD) diamond plate. For the case of the SiO2 films on a Si, we find an apparent thickness dependence of the thermal conductivity of the SiO2 films. However, the data can also be explained by a thickness-independent thermal conductivity and an interfacial thermal resistance. For the case of the CVD diamond plate, the fit of the theory to the experimental data is significantly improved if we assume that an interface layer separates the heater from the diamond plate.

Performance of multilayer thin-film multijunction thermal converters

New multilayer, thin-film multijunction thermal converters (MJTCs) suitable as high performance ac-dc transfer standards have been fabricated and studied at NIST. This paper describes their thermal and physical features and the materials chosen to improve performance. Performance data are given over a wide range of frequencies and conditions. >

Development of thin-film multijunction thermal converters at NIST

This paper gives an overview of the development of thin-film multijunction thermal converters (FMJTCs) at the National Institute of Standards and Technology (NIST). A historical perspective of film thermal converters is presented, followed by descriptions of the motivation, fabrication processes, physical characteristics, and the electrical properties of the FMJTCs produced at NIST. Integrated micropotentiometers that incorporate FMJTCs and thermal converters, produced by an alternative fabrication technology using a CMOS foundry, are also described. The paper concludes with a report on the present status of the FMJTC project and future directions.

Micromachined Silicon Torsional Resonator for Magnetic Anisotropy Measurement

A novel method for measuring the out-of-plane magnetic anisotropy of thin films has been developed using the existing techniques of silicon micromachining. The torsion pendulum, which is commonly used to measure the perpendicular magnetic anisotropy energy constant, Ku, is modified into a single crystal silicon high Q torsional resonator. This article describes the principle of a silicon torsional resonator, the experimental procedure for measuring magnetic anisotropy, and the results. The theoretical values of Ku for Terfenol-D and Metglas® thin films were compared to the experimentally determined values and found to be within the error limits which for Metglas©, better than 1%. The agreement is poorer, 5%–15%, for amorphous stressed Terfenol-D, since its magneto-elastic energy is less accurately known. The results show that this is a viable method for measuring the magnetic anisotropy.

Persistent photoconductivity in SIMOX film structures

Photoinduced transient spectroscopy (PITS) was used to measure the persistent photoconductive (PPC) response in n‐type separation by implanted oxygen (SIMOX) film resistors. A broadband, single‐shot, flashlamp‐pumped dye laser pulse was used to photoexcite interband electrons in the film, and the excess carrier population decay was measured at temperatures in the 60–220‐K range. The PPC signals exhibit nonexponential character and the conductivity transients are recorded as a function of temperature for variable periods up to 30 s. The photoconductive data are analyzed by using the Queisser and Theodorou potential barrier model, and a logarithmic time‐decay dependence is confirmed for the first time in SIMOX material. The hole‐trap density at the conductive‐film–buried‐silica interface is calculated to be in the high 1015 cm−3 to low 1016 cm−3 range. The sensitivity of PITS is demonstrated to be appropriate for characterization of the SIMOX interface structure and for material qualification.

Integrated thin-film micropotentiometers

Integrated micropotentiometers, new devices fabricated with thin-film technology and the micromachining of silicon, have been developed for the accurate determination of ac voltage from 1 to 200 mV at frequencies from audio to 1 MHz and with the potential for higher frequencies. >

An X-ray monochromator crystal which detects the bragg condition

Abstract We have fabricated a (111) silicon X-ray monochromator crystal with a diode diffused into its surface. Without suffering any apparent degradation in its or rocking-curve width at the Bragg condition, the crystal provides a dc current which changes dramatically at the diffraction of a monochromatic X-ray beam. The current change is directly attributable to extinction at the Bragg angle. It provides a new means to align the two crystals of a double-crystal X-ray monochromator using a feedback circuit.

High-current thin film multijunction thermal converters and multi-converter modules

High-current, thin-film multijunction thermal converters (FMJTCs) have been fabricated at NIST with heater ranges from a few milliamperes to 1 A. Multiconverter modules containing high-current FMJTCs have also been constructed to measure currents up to 6 A at frequencies up to 100 kHz.

Hybrid construction of multijunction thermal converters

Multijunction thermal converters designed for frequencies ranging from audio up to tens of megahertz and for heater currents from a few milliamperes up to hundreds of milliamperes, using thin-film and thick-film technologies, are described. Prototypes with various test features are reported. Different thermocouple geometries and guard couples have been included to investigate the heater temperature distribution and to study ways to optimize other characteristics. Different metals are also being investigated for use as the heater and thermocouples. The construction involves unsupported, dielectric membranes. Packages have been designed and fabricated to provide long-term stability, small distributed capacitance and inductance, and minimum skill effect through the use of all nonmagnetic materials.<<ETX>>

Advanced Sensors for Accurate, Broadband AC Voltage Metrology

We report on advances in ac voltage metrology made possible by a new generation of Multijunction Thermal Converters (MJTCs). Although intended for use primarily in high-frequency (1 MHz to 100 MHz) metrology, their exceptional low-frequency qualities, combined with a large dynamic range, makes these MJTCs excellent devices for the frequency range 10 Hz to 100 MHz at voltages from 1 V to 20 V, depending on the design. We anticipate that these devices will form the future basis for ac voltage metrology at the National Institute of Standards and Technology (NIST).