Inter- and intralayer compression of germanane

The inter- and intralayer compression in germanane (GeH) were investigated at room temperature and pressures up to 10 GPa using a diamond-anvil cell (DAC) in combination with X-ray diffraction and micro-Raman spectroscopy. To examine the effect of the pressure-transmitting medium (PTM) on the interlayer compression leading to a possible insertion and exfoliation, two separate experiments were performed using water as PTM and no PTM. The results indicate that both the inter- and intralayer compression are dependent on the PMT, and the linear compressibility is 0.0274(1) and 0.0031(9) GPa^-1 along the c- and a-axis based on the shifts of the (002) and (100) reflections for water PTM, and 0.0190(6) and 0.0026(9) GPa^-1 along the c- and a-axis when pressurizing without PTM. High-pressure Raman spectra indicate that the intralayer Ge-Ge stretching mode is also dependent on the PMT. It exhibits a blue-shift of 3.01 and 2.66 cm^-1/GPa when using water as PTM and without PTM, respectively. The equation of state determined from our experiments yields a bulk modulus of 9.6(2) GPa with B′₀ = 12 for GeH. Theoretical calculations were performed to understand the pressure dependence on the electronic band structure and the observed Raman spectrum.