Possible mechanisms for the introduction of hydrogen into alpha-quartz during sweeping

Gualtieri, J.G.

doi:10.1109/freq.1988.27596

Cited by 7 publications

(9 citation statements)

References 12 publications

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“…They can also nucleate the crystallizationof other crystalline phases [37,38], inducing stress fractures in the quartz [7].…”

Section: A Substitutionalimpuritiesmentioning

confidence: 99%

“…Rutherford backscattering (RBS) has been used to study the interfacial diffusion between metal layers of quartz resonator electrodes [34] and the indiffusion of electrode metals into quartz during sweeping [7]. The techniqye of RBS involves directing a beam of high energy He ions at the sample, where the primary effect of the anpact is to change the energy of a small fraction of the He by backscattering.…”

Section: E Surface Evaluationsmentioning

confidence: 99%

“…Besides the indiffusion of hydrogen, electrode-metal indiffusion may also assist in the reduction of etch channels [3]. However, aggregation of the electrode-0090-5607/89/0000-038 1 $ I .OO 0 1989 IEEE metal atoms contributes to the nucleation of other crystalline phases, with subsequent fracturing of the quartz [7]. Also, electrode-metal impurities have been shown to be coupled to ultrasonic vibrations in quartz, leading to considerable increases in internal loss [16].…”

Section: Introductionmentioning

confidence: 98%

“…Diffusion of these metal impurities is influenced by the gradient of vibrational stress [I 71. These unfavorable reports prompted the study of methods to suppress electrode diffusion through: reduction of Z-surface damage; changes in metallization type; and reductions in the magnitude of sweeping field [7,18]. The same suppressiontechniqueswere used to study their influence on etch-channel density and H-introduction [I 91.…”

Section: Introductionmentioning

confidence: 99%

“…Rutherford backscattering (RBS) [7]; secondary ion mass spectroscopy(S1MS) [8]; acousticloss measurements [9]; and infrared (IR) absorption spectroscopy [lo-141.…”

Section: Introductionmentioning

confidence: 99%

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Sweeping quartz crystals

Gualtieri

Proceedings., IEEE Ultrasonics Symposium

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Sweeping is a purification process that removes certain impurities and thereby improves the radiation sensitivity of quartz crystals. It is an electric field driven, high-temperature, solid-state diffusion process. The major steps of a typical sweeping process consist of: applying electrodesto the Z-surfacesof a lumberedquartz bar; applying voltage to the electrodesto produce an electricfield of approximately 1 kV/cm; heating the bar slowly either in air, vacuum, or in hydrogen containing or inert atmospheres to about 5 0 0 ' C; monitoring the current through the bar (as sweepingprogresses,the current decreases); when the current decays to some near-constant value, cooling the bar slowly to room temperature,and removing the voltage.Alkali-metal impurities, such as Li+ and Na' , are charge compensators for trivalent aluminum impurities in quartz. When sweeping is performed in air or H2, the alkalis diffuseto the cathode and are replaced by the indiffusion of hydrogen at the anode. The alkali-metal impurities are subsequently removed by lapping the Zsurfaces. The sweeping process also modifiesdislocations, reducing the tendencyfor formation of etch channels.Recent advances have involved the use of impurity characterizations, such as: electron spin resonance (ESR); acoustic loss measurements;and infrared absorption spectroscopy (IR). Future directions for technology enhancementwill probably involve: developmentof methodsto control theelectrode-quartz-gasinterface; use of H+ ion implantation techniquqand UV-stimulatedsweeping.

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“…They can also nucleate the crystallizationof other crystalline phases [37,38], inducing stress fractures in the quartz [7].…”

Section: A Substitutionalimpuritiesmentioning

confidence: 99%

Section: E Surface Evaluationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

“…Rutherford backscattering (RBS) [7]; secondary ion mass spectroscopy(S1MS) [8]; acousticloss measurements [9]; and infrared (IR) absorption spectroscopy [lo-141.…”

Section: Introductionmentioning

confidence: 99%

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Sweeping quartz crystals

Gualtieri

Proceedings., IEEE Ultrasonics Symposium

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Electrode effects in the sweeping of alpha quartz

Gualtieri¹,

Lareau²,

Eckart³

1990

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

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Experimental observations are described in the air-sweeping of alpha-quartz that reveal the introduction of hydrogen. Porous electrodes facilitate the indiffusion of hydrogen. By contrast, the use of thick, nonporous, strongly adherent Au/Cr electrodes causes a color-center front to advance from anode to cathode. Evidence is presented that indicates that: (1) color centers form beneath nonporous portions of the anode that correlate with the formation of Cr(2)O(3) on the metal surface and Cr-silicides at the metal-quartz interface, and (2) large-diameter clear striae form along the c-axis that correlate with small openings in the anode. These observations suggest that: (1) openings in the anode metallization are required for hydrogen introduction; (2) the electrochemical charge-transfer reaction, leading to hydrogen introduction, occurs at the gas-electrode-quartz boundary and spreads laterally by interfacial diffusion of hydrogen species; and (3) color centers form through the suppression of interfacial H-diffusion. Additionally, electrode-surface damage and high electric fields can result in undesirable electrode-metal indiffusion.

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Advances in high-Q piezoelectric resonator materials and devices

Ballato

Gualtieri

1994

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

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In order to compare piezoelectric materials and devices, an intrinsic parameter, the motional time constant tau(1)/sup (m/)=(omega/sub m/Q/sub m/)(-1) for a particular mode m is employed. The use of tau(1)/sup (m/) follows from the accommodation of acoustic loss in the elastic compliance/stiffness and the establishment of material coefficients that are elements of viscosity matrices. Alternative and fully equivalent definitions of tau(1) are given based on the RC time constant derived from the equivalent circuit representation of a crystal resonator, acoustic attenuation, logarithmic decrement, and viscosity or damping. For quartz devices, the variation of tau(1): for any simple thickness mode, for the Y'X shear mode for rotated Y-cuts, and with diameter-thickness ratio for AT-cuts is discussed. Other factors such as mounting loss and loss caused by crystal inhomogeneities (dislocations, defect positions in the resonator, and impurity migration under vibrational stress) are briefly considered with quartz devices as the model. Some new piezoelectric materials/material constants/devices are reviewed and their motional time constants are compared. A physical parameter, composed of acoustic velocity, piezoelectric coupling, and tau(1) is identified which aids in understanding the maximum frequency limitations of plate resonators.

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Possible mechanisms for the introduction of hydrogen into alpha-quartz during sweeping

Cited by 7 publications

References 12 publications

Sweeping quartz crystals

Sweeping quartz crystals

Electrode effects in the sweeping of alpha quartz

Advances in high-Q piezoelectric resonator materials and devices

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