Sputtering Behavior of P3HT under Low-Energy Monoatomic Projectile Bombardment: Insights from Molecular Dynamics Simulations

S Louerdi and T Mouhib and M Kanski and Z Postawa, JOURNAL OF PHYSICAL CHEMISTRY C, 127, 15785-15796 (2023).

DOI: 10.1021/acs.jpcc.3c03203

Molecular dynamiccomputer simulations have been employed to investigatethe sputtering process of multilayer poly(3-hexylthiophene) (P3HT)with a layered structure arranged in the Z-directiondeposited on a silicon substrate. The sputtering process was inducedby low-energy He, Ar, and Xe projectiles. The sputtering yield volume,mass spectra, and structural and chemical damages induced in the bombardedsystems are probed depending on the type of projectile and the thicknessof the organic overlayer. While most studies are performed with a500 eV primary kinetic energy and an impact angle of 45 & DEG;, theeffect of these two parameters on the sputtering yield is investigatedfor the Ar projectile. The main goal is to elucidate the influenceof various primary beam properties on the sputtering process and structuraland chemical damages occurring in P3HT. The implications of the presentresults for the chemical analysis of P3HT by secondary ion mass spectrometry(SIMS) or secondary neutral mass spectrometry (SNMS) and low-energyatomic projectiles are discussed. It has been found that the sputteringyield volume is the largest for Ar and the smallest for He. The yielddoes not depend on the organic overlayer thickness within the computationaluncertainty. The number of ejected atoms scaled to the sample atomicdensity decreases monotonically with depth. Interestingly, the shapeof this distribution, known as the information depth distribution,is the same for all investigated projectiles, regardless of theirpenetration range, which indicates that this quantity is determinedby the properties of the sample. Additionally, the projectiles arenot deposited equally in the sample volume but are trapped at organic/substrateand interlayer interfaces. The vertical extent of damage is directlyrelated to the projectile range, which is the largest for He and thesmallest for Xe. The shape of vertical damage distribution dependsin an oscillatory manner on depth. It is shown that the alkyl sidechains are mostly damaged. Our results indicate that among all testedprojectiles, Ar, followed by Xe, are the best candidates for the chemicalanalysis of P3HT by SIMS/SNMS techniques.

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