Ge interactions on $HfO2$ surfaces and kinetically driven patterning of Ge nanocrystals on $HfO2$

Germanium interactions are studied on $HfO2$ surfaces, which are prepared through physical vapor deposition (PVD) and by atomic layer deposition. X-ray photoelectron spectroscopy and temperature-programed desorption are used to follow the reactions of germanium on $HfO2$⁠. Germanium chemical vapor deposition at 870 K on $HfO2$ produces a $GeOx$ adhesion layer, followed by growth of semiconducting $Ge0$⁠. PVD of 0.7 ML Ge (accomplished by thermally cracking $GeH4$ over a hot filament) also produces an initial $GeOx$ layer, which is stable up to 800 K. PVD above 2.0 ML deposits semiconducting $Ge0$⁠. Temperature programed desorption experiments of $∼1.0ML$ Ge from $HfO2$ at 400–1100 K show $GeH4$ desorption below 600 K and GeO desorption above 850 K. These results are compared to Ge on $SiO2$ where GeO desorption is seen at 550 K. Exploiting the different reactivity of Ge on $HfO2$ and $SiO2$ allows a kinetically driven patterning scheme for high-density Ge nanoparticle growth on $HfO2$ surfaces that is demonstrated.