TY  - CONF
AU  - Wulff, Harm
AU  - Quaas, M.
AU  - Deutsch, H.
AU  - Ahrens, Heiko
AU  - Fröhlich, M.
AU  - Helm, Christiane A.
TI  - Formation of palladium hydrides in low temperature Ar/H<sub>2</sub>-plasma
JO  - Thin solid films
VL  - 596
SN  - 0040-6090
CY  - Amsterdam [u.a.]
PB  - Elsevier
M1  - PUBDB-2016-02253
SP  - 185-189
PY  - 2015
AB  - 20 nm thick Pd coatings deposited on Si substrates with 800 nm SiO<sub>2</sub> and 1 nm Cr buffer layers were treated in a 2.45 GHz microwave plasma source at 700 W plasma power and 40 Pa working pressure without substrate heating. For obtaining information on the effect of energy influx due to ion energy on the palladium films the substrate potential was varied from U<sub>sub</sub> = 0 V to − 150 V at constant gas flow corresponding to mean ion energies E<sub>i</sub> from 0.22 eV ∙ cm<sup>− 2</sup> ∙ s<sup>− 1</sup> to 1.28 eV ∙ cm<sup>− 2</sup> ∙ s<sup>− 1</sup>.In contrast to high pressure reactions with metallic Pd, under plasma exposure we do not observe solid solutions over a wide range of hydrogen concentration. The hydrogen incorporation in Pd films takes place discontinuously. At 0 V substrate voltage palladium hydride is formed in two steps to PdH<sub>0.1</sub>4 and PdH<sub>0.57</sub>. At − 50 V substrate voltage Pd<sub>H0.57</sub> is formed directly. However, substrate voltages of − 100 V and − 150 V cause shrinking of the unit cell. We postulate the formation of two fcc vacancy palladium hydride clusters PdH<sub>Vac</sub>(I) and PdH<sub>Vac</sub>(II). Under longtime plasma exposure the fcc PdHVac(II) phase forms cubic PdH<sub>1.33</sub>.The fcc PdH<sub>0.57</sub> phase decomposes at temperatures > 300 °C to form metallic fcc Pd. The hydrogen removal causes a decrease of lattice defects. In situ high temperature diffractometry measurements also confirm the existence of PdHVac(II) as a palladium hydride phase. Stoichiometric relationship between cubic PdH<sub>1.33</sub> and fcc PdH<sub>Vac</sub>(II) becomes evident from XR measurements and structure considerations. We assume both phases have the chemical composition Pd<sub>3</sub>H<sub>4</sub>. Up to 700 °C we observe phase transformation between both the fcc PdH<sub>Vac</sub>(II) and cubic PdH<sub>1.33</sub> phases. These phase transformations could be explained analog to a Bain distortion by displacive solid state structural changes.
T2  - 42nd International Conference on Metallurgical Coatings and Thin Films
CY  - 20 Apr 2015 - 24 Apr 2015, San Diego (USA)
Y2  - 20 Apr 2015 - 24 Apr 2015
M2  - San Diego, USA
LB  - PUB:(DE-HGF)16 ; PUB:(DE-HGF)8
UR  - <Go to ISI:>//WOS:000366204900031
DO  - DOI:10.1016/j.tsf.2015.08.061
UR  - https://bib-pubdb1.desy.de/record/300271
ER  -