Effect of Thermal Annealing on Structure and Optical Properties of Poly(p-xylylene)–PbS Thin Films

Abstract

In this study, wide-angle X-ray diffraction, X-ray absorption spectroscopy, and transmission electron microscopy were employed to address the crystalline structure and morphology of poly(p-xylylene)−PbS nanocomposite thin films prepared by vapor deposition polymerization as well as their evolution upon thermal annealing. It was found that as-synthesized samples with different PbS contents demonstrate similar diffraction patterns that cannot be fully ascribed to a decrease in crystallite size, indicating distorted crystal structure of PbS nanoparticles compared to the bulk PbS. X-ray absorption spectroscopy reveals wide distribution of Pb−S bond lengths with a minimum value of 2.67 Å, which can be attributed to the presence of molecular (PbS) n clusters in the studied films. It was shown that thermal annealing can be used to control the size of PbS nanoparticles and, as a consequence, optical properties of the composite films. The UV−vis absorption spectra demonstrate pronounced red shift of the absorption edge correlated with the growth of PbS nanoparticles upon annealing. Comprehensive analysis of several theoretical models describing the effect of nanoparticles size on optical band gap of the composite material has been performed and compared with the experimental data.

Structural characterization and magnetic response of poly(p-xylylene)–MnSb and MnSb films deposited at cryogenic temperature

“…In particular, using poly( p -xylylene) (PPX) as a matrix provides the possibility to obtain flexible and bio-compatible nanocomposites. Various PPX-based nanocomposites with metallic 21 , 22 , semiconducting 23 , 24 and magnetic 25 , 26 fillers were successfully synthesized using low-temperature vapor deposition polymerization (VDP) method 27 . Aside from primary properties variations, such nanocomposites are promising for applications due to their gas-sensing 28 and memristive 29 properties, while magnetic hybrid nanocomposites also can be used for spintronic applications.…”

“…It should be noted that the presence of surface oxide layer may increase the coercive force of the MnSb film due to locally randomized exchange bias phenomenon 30 . Low-temperature VDP route implies the deposition on the substrate held at cryogenic temperatures, which may lead to the formation of nanoinclusions with distorted crystal structure or even molecular clusters 24 , affecting the resultant properties of the nanocomposite. At cryogenic temperatures the formation of binary phase inclusions (e.g.…”

“…At cryogenic temperatures the formation of binary phase inclusions (e.g. MnSb) from elemental precursors seems to have rather low probability, which is why for VDP synthesis binary precursors seem to be more suitable 23 , 24 . However, for MnSb the effects of such deposition conditions, let alone the incorporation into organic matrix, have not been studied in detail yet.…”

Влияние наполнителя на ИК-спектры полимерных нанокомпозитов поли-n-ксилилен-сульфиды

“…Для пленочных нанокомпозитов в качестве полимерной матрицы широко используется поли-п-ксилилен (ППК) [1][2][3][4][5], а в качестве наполнителя -полупроводниковые наночастицы сульфида свинца (PbS) [6][7][8] или сульфида кад-мия (CdS) [9][10][11], обладающие высокой фоточувствительностью в ИК и видимом диапазоне соответственно и традиционно использующиеся для создания фотоизлучателей и фотоприемников [12,13]. Пленки ППК, содержащие наночастицы PbS или CdS, могут использоваться как функциональные элементы для оптоэлектроники, сенсорной техники и энергетики.…”

“…В [18][19][20] отмечалось, что некоторые металлы и их соли ингибируют процесс полимеризации п-ксилилена из-за образования слабосвязанных комплексов между металлом и радикальным концом растущей цепи полимера. При исследованиях пленок ППК, содержащих наночастицы сульфида кадмия определенной концентрации, выявлены нарушения чередования плоскостей упаковки в наночастицах CdS [10], а в пленках ППК, содержащих наночастицы сульфида свинца, обнаружено одновременное присутствие наночастиц PbS и молекулярных кластеров (PbS) n [8]. Также в нанокомпозитах ППК-PbS [6] при концентрации C ~ 8.5 об.…”