@article{christman_kim_maiwa_maria_rodriguez_kingon_nemanich_2000, title={Spatial variation of ferroelectric properties in Pb(Zr-0.3, Ti-0.7)O-3 thin films studied by atomic force microscopy}, volume={87}, ISSN={["0021-8979"]}, DOI={10.1063/1.373492}, abstractNote={Imaging of the phase and magnitude of the piezoelectric strain in Pb(Zr0.3, Ti0.7)O3 (PZT) capacitors is performed with an atomic force microscope. The imaging reveals a significant spatial dependence of the ferroelectric properties of both fatigued and unfatigued PZT films. We propose that the variation is related to the domain structure of the PZT. Through the measurement of local piezoelectric hysteresis loops and imaging of the piezoelectric strain, areas are observed in fatigued PZT that exhibit hysteresis loops shifted along the polarization axis. In some regions of fatigued samples, the hysteresis loops are shifted such that both remanent points of the hysteresis curve have the same polarization direction. These results have important implications for the scalability of nonvolatile ferroelectric random access memory to higher device densities.}, number={11}, journal={JOURNAL OF APPLIED PHYSICS}, author={Christman, JA and Kim, SH and Maiwa, H and Maria, JP and Rodriguez, BJ and Kingon, AI and Nemanich, RJ}, year={2000}, month={Jun}, pages={8031–8034} }
 @article{maiwa_maria_christman_kim_streiffer_kingon_1999, title={Measurement and calculation of PZT thin film longitudinal piezoelectric coefficients}, volume={24}, ISSN={["1058-4587"]}, DOI={10.1080/10584589908215586}, abstractNote={The ferroelectric and piezoelectric properties of 2000 {angstrom} thick chemical solution deposited Pb(Zr{sub x}Ti{sub 1{minus}x})O{sub 3} (PZT) thin films were investigated. Several Zr/Ti ratios were studied: 30/70, 50/50 and 65/35, which correspond to tetragonal, near-morphotropic, and rhombohedral symmetries. In all samples, a {l_brace}111{r_brace}-texture is predominant. Longitudinal piezoelectric coefficients and their dc field dependence were measured using the contact AFM method. The expected trend of a maximum piezoelectric coefficient at or near to the MPB was not observed. The composition dependence was small, with the maximum d{sub 33} occurring in the tetragonal material. To explain the results, crystallographic texture and film thickness effects are suggested. Using a modified phenomenological approach, derived electrostrictive coefficients, and experimental data, d{sub 33} values were calculated. Qualitative agreement was observed between the measured and calculated coefficients. Justifications of modifications to the calculations are discussed.}, number={1-4}, journal={INTEGRATED FERROELECTRICS}, author={Maiwa, H and Maria, JP and Christman, JA and Kim, SH and Streiffer, K and Kingon, AI}, year={1999}, pages={139–146} }
 @article{maiwa_christman_kim_kim_maria_chen_streiffer_kingon_1999, title={Measurement of piezoelectric displacements of Pb(Zr, Ti)O-3 thin films using a double-beam interferometer}, volume={38}, ISSN={["0021-4922"]}, DOI={10.1143/jjap.38.5402}, abstractNote={ 
  The double-beam interferometric method is applied to measure the field-induced  
  displacement of Pb(Zr, Ti)O3 thin films. The dc electric field dependence of the  
  longitudinal piezoelectric coefficient (d
                  33) response of Pb(Zr, Ti)O3 thin films deposited  
  by metal organic chemical vapor deposition (MOCVD) was measured. Experimental d
                  33  
  values were compared with coefficients calculated using a phenomenological approach  
  and bulk parameters. Qualitative agreement was obtained between measured and  
  calculated coefficients. 
  }, number={9B}, journal={JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS}, author={Maiwa, H and Christman, JA and Kim, SH and Kim, DJ and Maria, JP and Chen, B and Streiffer, SK and Kingon, AI}, year={1999}, month={Sep}, pages={5402–5405} }
 @article{bergman_dutta_balkas_davis_christman_alexson_nemanich_1999, title={Raman analysis of the E1 and A1 quasi-longitudinal optical and quasi-transverse optical modes in wurtzite AlN}, volume={85}, ISSN={["0021-8979"]}, DOI={10.1063/1.369712}, abstractNote={This article presents a study of the quasi-longitudinal optical and quasi-transverse optical modes in wurtzite AlN which originate from the interaction of phonons belonging to the A1 and E1 symmetry groups. In order to analyze the allowed quasi as well as pure Raman modes, the modes were observed in a rotating crystallographic coordinate system, and the Raman tensors of the wurtzite crystal structure were calculated as a function of the crystallographic rotation. The frequencies of the quasimodes of wurtzite AlN were also analyzed in terms of the interaction of the polar phonons with the long range electrostatic field model. The experimental values of the Raman frequencies of the quasiphonons concur with these expected from the model, implying that the long range electrostatic field dominates the short range forces for polar phonons in AlN.}, number={7}, journal={JOURNAL OF APPLIED PHYSICS}, author={Bergman, L and Dutta, M and Balkas, C and Davis, RF and Christman, JA and Alexson, D and Nemanich, RJ}, year={1999}, month={Apr}, pages={3535–3539} }
 @article{king_carlson_therrien_christman_nemanich_davis_1999, title={X-ray photoelectron spectroscopy analysis of GaN/(0001)AlN and AlN/(0001)GaN growth mechanisms}, volume={86}, ISSN={["0021-8979"]}, DOI={10.1063/1.371564}, abstractNote={The mechanisms of growth of GaN on AlN and AlN on GaN via gas source-molecular beam epitaxy with NH3 as the nitrogen source have been investigated using x-ray photoelectron spectroscopy, low energy electron diffraction, and Auger electron spectroscopy. The growth of GaN on AlN at low temperatures (650–750 °C) occurs via a Stranski–Krastanov 2D→3D type mechanism with the transition to 3D growth occurring at ≈10–15 Å. The mechanism changes to Frank van der Merwe (FM)/layer-by-layer growth above 800 °C. The growth of AlN on GaN occurred via a FM layer-by-layer mechanism within the 750–900 °C temperature range investigated. We propose a model based on the interaction of ammonia and atomic hydrogen with the GaN/AlN surfaces which indicates that the surface kinetics of hydrogen desorption and ammonia decomposition are the factors that determine the GaN growth mechanism.}, number={10}, journal={JOURNAL OF APPLIED PHYSICS}, author={King, SW and Carlson, EP and Therrien, RJ and Christman, JA and Nemanich, RJ and Davis, RF}, year={1999}, month={Nov}, pages={5584–5593} }
 @article{christman_woolcott_kingon_nemanich_1998, title={Piezoelectric measurements with atomic force microscopy}, volume={73}, ISSN={["0003-6951"]}, DOI={10.1063/1.122914}, abstractNote={An atomic force microscope (AFM) is used to measure the magnitude of the effective longitudinal piezoelectric constant (d33) of thin films. Measurements are performed with a conducting diamond AFM tip in contact with a top electrode. The interaction between the tip and electric field present is a potentially large source of error that is eliminated through the use of this configuration and the conducting diamond tips. Measurements yielded reasonable piezoelectric constants of X-cut single-crystal quartz, thin film ZnO, and nonpiezoelectric SiO2 thin films.}, number={26}, journal={APPLIED PHYSICS LETTERS}, author={Christman, JA and Woolcott, RR and Kingon, AI and Nemanich, RJ}, year={1998}, month={Dec}, pages={3851–3853} }
 @article{christensen_donaldson_nestor_1997, title={Effects of an oxygen-enriched environment on the survival of turkey embryos between twenty-five and twenty-eight days of age}, volume={76}, ISSN={["0032-5791"]}, DOI={10.1093/ps/76.11.1556}, abstractNote={The hypothesis was tested that increased partial pressure of oxygen during the plateau (25 to 26 d of incubation for turkeys) and paranatal (27 to 28 d of incubation) stages of incubation may increase survival rates of turkeys from selected genetic lines. Partial pressure of oxygen inside the incubator cabinet was increased to 171 + 3 mm Hg of the barometric pressure during the plateau stage in oxygen consumption and compared to ambient oxygen (152 + 3 mm Hg). Turkey embryos from genetic lines selected for egg production (E) or growth (F) were compared to their respective randombred controls. These genetic lines have previously been shown to differ in egg weight, eggshell conductance, length of incubation period, embryonic gluconeogenesis, and survival rates during late incubation. Blood, liver, heart, and pipping muscle samples were obtained prior to pipping, at internal pipping and external pipping, and at hatching. The blood was analyzed for glucose concentration and the remaining tissues were assayed for glycogen concentrations. Survival rates were determined on approximately 2,200 eggs in each of three independent trials of the experiment. Interactions of oxygen treatment and genetic line were observed for embryonic survival, heart growth, and hepatic glycogen content. The data suggest that the response to increased oxygen tension in selected genetic lines has been diminished. It was concluded that embryos have been altered metabolically by genetic selection and the concomitant increase in mortality of selected lines during the plateau and paranatal stages is not simply the result of shell quality and hypoxia.}, number={11}, journal={POULTRY SCIENCE}, author={Christensen, VL and Donaldson, WE and Nestor, KE}, year={1997}, month={Nov}, pages={1556–1562} }
 @article{fan_croom_christensen_black_bird_daniel_mcbride_eisen_1997, title={Jejunal glucose uptake and oxygen consumption in turkey poults selected for rapid growth}, volume={76}, ISSN={["0032-5791"]}, DOI={10.1093/ps/76.12.1738}, abstractNote={Two lines of turkey poults, one selected for rapid growth at 16 wk of age (F line) and the other a randombred control line (RBC2) were used to investigate the effect of selection for rapid growth on jejunal O2 consumption and glucose transport as well as whole-body O2 consumption. All trials used unsexed poults and were designed as a randomized complete block with day and line as independent variables. In Trial 1, 120 turkey poults, fed a standard starter ration (25.5% CP), were used to examine the effect of selection on feed intake, body weight gain, and efficiency from hatching (Day 0) to 13 d of age. At Day 14, 36 of 60 birds from each line were killed to measure intestinal length and weight and jejunal O2 consumption after 18 h of feed deprivation. Compared with the RBC2 line, the F line had relatively shorter but heavier small intestinal segments when adjusted by 18 h feed-deprived body weight (FBW; P < 0.001). The F line consumed more O2 over the entire jejunum adjusted to FBW than RBC2 line (43.8 vs 34.6 nmol O2/min.g FBW; P < 0.001). Jejunal ouabain- and cycloheximide-sensitive O2 consumption were greater (P < 0.05) in the F line. In Trial 2, 16 14-d-old poults from each line were used to measure in vitro jejunal glucose transport rate. There was no difference in glucose transport of the jejunum (nanomoles per minute per gram of FBW) between the lines. In Trial 3, 20 poults from each line were used to measure whole-body O2 consumption at 7 to 10 d of age. The F and RBC2 lines had similar whole-body O2 consumption rate per gram of FBW. These data suggest that selection of turkeys for rapid growth at 16 wk of age did not increase efficiency of jejunal glucose uptake in 14-d-old turkey poults.}, number={12}, journal={POULTRY SCIENCE}, author={Fan, YK and Croom, J and Christensen, VL and Black, BL and Bird, AR and Daniel, LR and McBride, BW and Eisen, EJ}, year={1997}, month={Dec}, pages={1738–1745} }
 @article{sowers_christman_bremser_ward_davis_nemanich_1997, title={Thin films of aluminum nitride and aluminum gallium nitride for cold cathode applications}, volume={71}, DOI={10.1063/1.120052}, abstractNote={Cold cathode structures have been fabricated using AlN and graded AlGaN structures (deposited on n-type 6H-SiC) as the thin film emitting layer. The cathodes consist of an aluminum grid layer separated from the nitride layer by a SiO2 layer and etched to form arrays of either 1, 3, or 5 μm holes through which the emitting nitride surface is exposed. After fabrication, a hydrogen plasma exposure was employed to activate the cathodes. Cathode devices with 5 μm holes displayed emission for up to 30 min before failing. Maximum emission currents ranged from 10–100 nA and required grid voltages ranging from 20–110 V. The grid currents were typically 1 to 104 times the collector currents.}, number={16}, journal={Applied Physics Letters}, author={Sowers, A. T. and Christman, J. A. and Bremser, M. D. and Ward, B. L. and Davis, R. F. and Nemanich, R. J.}, year={1997}, pages={2289–2291} }