Abstract
Multi-material systems interfaced with 2D materials, or entirely new 3D heterostructures can lead to the next generation multi-functional device architectures. Physical and chemical control at the nanoscale is also necessary tailor these materials as functional structures approach physical limit. 2D transition metal thiophosphates (TPS), with a general formulae Cu1−xIn1+x/3P2S6, have shown ferroelectric polarization behavior with a Tc above the room temperature, making them attractive candidates for designing both: chemical and physical properties. Our previous studies have demonstrated that ferroic order persists on the surface, and that spinoidal decomposition of ferroelectric and paraelectric phases occurs in non-stoichiometric Cu/In ratio formulations. Here, we discuss the chemical changes induced by helium ion irradiation. We explore the TPS compound library with varying Cu/In ratio, using Helium Ion Microscopy, Atomic Force Microscopy (AFM), and Time of Flight-Secondary Ion Mass Spectrometry (ToF-SIMS). We correlate physical nano- and micro- structures to the helium ion dose, as well as chemical signatures of copper, oxygen and sulfur. Our ToF-SIMS results show that He ion irradiation leads to oxygen penetration into the irradiated areas, and diffuses along the Cu-rich domains to the extent of the stopping distance of the helium ions.
Highlights
Resist-based lithography is currently the mainstay of nanostructure fabrication, resist free nanofabrication directly on the surface is bringing electron, ion, and probe technologies to the forefront[8,9,10]
The TPS samples were mounted on conductive carbon tape (PELCO Tabs, Ted Pella 16084-3) and grounded via stainless steel pucks in Atomic Force Microscopy (AFM) and Helium Ion Microscope (HIM) experiments
Oxidation may occur within the HIM chamber immediately as the TPS surface is exposed to the beam
Summary
Resist-based lithography is currently the mainstay of nanostructure fabrication, resist free nanofabrication directly on the surface is bringing electron, ion, and probe technologies to the forefront[8,9,10]. We demonstrate HIM to create a variety of micro-sized structures with varying chemical properties atop several transition metal thiophosphates (TPS); a broad class of van-der-Waals layered solids[10,13,23]. TPS exhibit strong ionic character in the chemical bonds between transition metals and the P2S6 framework[24] These compounds have large band-gaps and a pronounced flexibility in ionic substitution of the metal sites; with over 260 combinations known for the sulfides alone. Some of these compounds support coherent ordering of metal ions across layers, with ferroelectric and anitferroelectric ground states[14,15], dielectric relaxor behavior[16,17], and associated phase transitions. Our results demonstrate that copper concentration dictates the sizes of the nanostructures, as the same helium dose applied to the same area yields different volumes in the final protrusions
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
