FTIR studies on polymorphic control of PVDF ultrathin films by heat-controlled spin coater

The performance of organic polymer-based memory devices based on polyvinylidene fluoride (PVDF) ultrathin films depends on the extent of its ferroelectric crystalline phase content. In the present study, the changes in polymorphs of PVDF ultrathin films prepared by using heat-controlled spin coater are examined. The polymorphic changes were analyzed by using FTIR-transmission (TS) and FTIR-grazing incidence reflection–absorption spectroscopy (GIRAS) as a function of varying (i) spin-coating temperatures (SCT-30 to 80 °C), (ii) spin-coating substrates (KBr, ITO and Gold) and (iii) thermal treatments [as-cast (AC) at 30 °C, annealed at 130 °C (AN130) and melt (200 °C)-slow cooled (MSC)] conditions. Compared to MSC samples, the AC and AN130 samples exhibited higher β-crystalline (polar, all-trans) phase along with the complete absence of α-crystalline (non-polar, tgtg′) phase at lower SCT-30 and 40 °C irrespective of the substrates used, thereby avoiding the need of high-temperature SCT conditions. Among the three substrates used, FTIR-GIRAS data obtained using ITO and Gold substrates were more favored than the FTIR-TS data obtained using KBr window due to their real-time usage as the substrate for electronic applications.