Molecular Doping (MD) involves the deposition of molecules, containing the dopant atoms and dissolved in liquid solutions, over the surface of a semiconductor before the drive-in step. The control on the characteristics of the final doped samples resides on the in-depth study of the molecule behaviour once deposited. It is already known that the molecules form a self-assembled monolayer over the surface of the sample, but little is known about the role and behaviour of possible multiple layers that could be deposited on it after extended deposition times. In this work, we investigate the molecular surface coverage over time of diethyl-propyl phosphonate on silicon, by employing high-resolution morphological and electrical characterization, and examine the effects of the post-deposition surface treatments on it. We present these data together with density functional theory simulations of the molecules–substrate system and electrical measurements of the doped samples. The results allow us to recognise a difference in the bonding types involved in the formation of the molecular layers and how these influence the final doping profile of the samples. This will improve the control on the electrical properties of MD-based devices, allowing for a finer tuning of their performance.
Bibliografisk noteFunding Information:
Acknowledgments: We acknowledge Salvo Di Franco and Markus Italia (CNR-IMM) for their valuable work during the samples synthesis and characterization. R.A.P. and M.P. wish to mention the funding from the National Research Council (CNR) and STMicroelectronics s.r.l. as part of the CNR-Confindustria Project for Industrial PhDs. The computational calculations contributing to this work were carried out with support of the UCloud services provided by the eScience Center at SDU.
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