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In this work, the so-called hot-wire (HW) assisted atomic layer deposition (HWALD) technique is employed to grow high-purity α-phase tungsten (W) films at a substrate temperature of 275°C. The films are deposited on thermally grown silicon dioxide (SiO 2 ) in a home-built hot-wall reactor, using alternating pulses of WF 6 and HWgenerated atomic hydrogen in the self-limiting surface-reaction manner characteristic for ALD. A W seed layer, needed to enable the HWALD-W process on a SiO 2 surface, is formed prior to each deposition. In-situ spectroscopic ellipsometry is used to monitor the growth behavior and film properties. The films exhibit a high-purity (99 at.%) W, according to X-ray photoelectron spectroscopy. The X-ray diffraction scans reveal the existence of α-phase W. The resistivity measurements by means of four point probe, transfer length method test structures and the Drude-Lorentz SE model all reveal a low resistivity of 15 μΩ•cm. The high-resolution transmission electron microscopy analysis shows a uniform and conformal coverage of high aspect ratio structures, confirming the effective ALD process and the sufficient diffusion of both WF 6 and at-H into deep trenches.

An extensive post‐mortem analysis was conducted on a commercial copper‐(indium‐gallium)‐diselenide (CIGS) photovoltaic module that degraded after exposure to the high voltage stress of a standardized potential induced degradation (PID) test. We employed a custom‐developed coring technique to extract samples from the full‐size field module, which showed degraded and nondegraded areas (regarded as reference) in electroluminescence after the PID test. The resulting solar cell samples were compared based on their electrical properties and sodium profiles using a wide range of laboratory‐based analysis techniques including photoluminescence and lock‐in thermography imaging, current–voltage measurements, and glow discharge optical emission spectroscopy. The samples that were extracted from the degraded areas of the module showed lower photoluminescence intensity and had significantly lower open‐circuit voltage V(oc) and fill factor (FF) values in comparison with reference samples. An increased content of sodium within the absorber layer was also observed for these samples, linking sodium migration to PID. These observations at the module level are consistent with earlier reports on PID‐stressed CIGS cells and mini‐modules. This is to our knowledge the first reported study of a microscopic investigation on a real‐life full‐scale CIGS module after PID.