Capacitance Effects in Thin Conductive Films

Humphrey, James N.; Lummis, Frances L.; Scanlon, Wayne W.

doi:10.1103/physrev.90.111

Cited by 19 publications

(7 citation statements)

References 3 publications

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“…Based on humphrey's report [36], assuming the rF resistivity of the film is an order of magnitude lower than the dc value (0.125 Ω-cm) is a conservative estimate. Using the rF resistivity value (0.0125 Ω-cm) and the measured propagation loss data, the aE model implies an effective permittivity of 7 × 10 6 before hydrogen gas exposure and an increase to 7 × 10 7 after final hydrogen gas exposure.…”

Section: B Saw Pd Thin Film Experimental Resultsmentioning

confidence: 99%

“…The effects of a low rF resistivity and high effective permittivity on the aE response are complementary, because a decrease in resistivity shifts the dielectric relaxation frequency upward, whereas a high effective permittivity shifts the relaxation frequency downward. The saW-film interaction occurs at the micron and submicron level because of the saW wavelength and film morphology; thus it is not clear whether the rF resistivity and effective permittivity observed using the EM waves [36]- [39] will be the same when observed with a saW. These parameters change when an ultra-thin Pd film is exposed to hydrogen gas, and may dramatically alter the aE response of the saW.…”

Section: ) Pd Ultra-thin Film Reviewmentioning

confidence: 90%

“…humphrey et al [36] reported a frequency dependent resistivity for nano-clustered films. humphrey's experiments showed that the resistivity decreased by as much as 3 orders of magnitude as frequency is increased from 10 khz to 200 Mhz.…”

Section: ) Pd Ultra-thin Film Reviewmentioning

confidence: 98%

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Study of the acoustoelectric effect for SAW sensors

Fisher

Malocha

2010

IEEE Trans. Ultrason., Ferroelect., Freq. Contr.

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Research has recently begun on the use of ultrathin films and nanoclusters as mechanisms for sensing of gases, liquids, etc., because the basic material parameters may change because of film morphology. As films of various materials are applied to the surface of SAW devices for sensors, the conductivity of the films may have a strong acoustoelectric effect, whether desired or not. The purpose of this paper is to reexamine the theory and predictions of the acoustoelectric effect for SAW interactions with thin conducting or semi-conducting films. The paper will summarize the theory and predict the effects of thin film conductivity on SAW velocity and propagation loss versus frequency and substrate material. The theory predicts regions of conductivity which result in extremely high propagation loss, and which also correspond to the mid-point between the open and short-circuit velocities. As an example of the verification and possible usefulness of the acoustoelectric effect, recent experimental results of palladium (Pd) thin films on a YZ LiNbO3 SAW delay line have shown large changes in propagation loss, depending on the Pd film thickness, exposure to hydrogen gas, or both. By proper design, a sensitive hydrogen leak detector SAW sensor can be designed.

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Section: B Saw Pd Thin Film Experimental Resultsmentioning

confidence: 99%

Section: ) Pd Ultra-thin Film Reviewmentioning

confidence: 90%

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Study of the acoustoelectric effect for SAW sensors

Fisher

Malocha

2010

IEEE Trans. Ultrason., Ferroelect., Freq. Contr.

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“…In the literature, the observations of high effective permittivity in discontinuous metal films were documented at electromagnetic (EM) wavelengths and velocities, which are 3 × 10 5 times smaller and faster, respectively, than saWs. The interaction of the ultra-thin film and the saW appears to be electrostatic, whereas, for an EM wave, discontinuous films may be modeled as a network of resistors and capacitors [17] which yields differing results.…”

Section: Ultra-thin Film Dispersionmentioning

confidence: 98%

In situ observation and measurement of the SAW thin-film acoustoelectric effect

Fisher

Malocha

2012

IEEE Trans. Ultrason., Ferroelect., Freq. Contr.

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The thin-film acoustoelectric effect in SAW devices describes the interaction of electrical energy between a SAW in a piezoelectric medium and a thin film in the wave's propagation path. The real-time observation of the thin-film acoustoelectric interaction is useful in the design and characterization of SAW sensors (i.e., temperature, humidity, viscosity, voltage, current, Hall effects, etc.). An in situ test fixture was designed to be mechanically, thermally, and electrically stable. Data acquisition software and an electron beam evaporation system were configured for real-time thin-film characterization during film growth. Data have been observed for more than 20 SAW devices and over a wide range of frequencies (i.e., 62 MHz to 1 GHz). The results suggest that the use of the in situ procedure yielded good agreement between theoretical predictions and the measured data, which demonstrates a method for the characterization of a SAW H(2)-gas sensor in real-time.

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“…In this methodology, the frequency response of the material is analyzed by using equivalent circuit. It has provided evidence to identify the relaxation mechanisms of the electric properties, contributed by grains, grain boundaries or macroscopic heterogeneities [9][10][11]. In the present study, the frequency response of discontinuous [Co 80 Fe 20 /a-Fe 2 O 3 ] 10 multilayers has been investigated using impedance spectroscopy.…”

Section: Introductionmentioning

confidence: 96%