Fig. 3: Microscopy and spectroscopy of tantalum films.

a STEM image of the tantalum film, showing single-crystal columns with the growth direction oriented along the [110] axis. b Atomic-resolution STEM image of an interface between two columns, viewed from \(\left\langle 1\bar{1}1\right\rangle\) and \(\left\langle 001\right\rangle\) zone axes, respectively. Fourier transforms (insets) of the image show that the columns are oriented with the image plane perpendicular to the \(\left\langle 111\right\rangle\) or \(\left\langle 100\right\rangle\) directions. c STEM image of a horizontal device cross section, showing grain boundaries. Image contrast at grain boundaries results from diffraction contrast caused by interfacial defects. d XPS spectrum of a device, exhibiting peaks from tantalum metal and Ta₂O₅. Other oxidation states of tantalum are expected to have binding energies between 22.2 and 23.8 eV^{42, 43}. e High-resolution STEM with integrated differential phase contrast imaging of the interface between the sapphire and tantalum showing epitaxial growth.