Molecule-by-Molecule Writing Using a Focused Electron Beam

The resolution of lithography techniques needs to be extended beyond their current limits to continue the trend of miniaturization and enable new applications. But what is the ultimate spatial resolution? It is known that single atoms can be imaged with a highly focused electron beam. Can single atoms also be written with an electron beam? We verify this with focused electron-beam-induced deposition (FEBID), a direct-write technique that has the current record for the smallest feature written by (electron) optical lithography. We show that the deposition of an organometallic precursor on graphene can be followed molecule-by-molecule with FEBID. The results show that mechanisms that are inherent to the process inhibit a further increase in control over the process. Hence, our results present the resolution limit of (electron) optical lithography techniques. The writing of isolated, subnanometer features with nanometer precision can be used, for instance, for the local modification of graphene and for catalysis

Molecule-by-Molecule Writing Using a Focused Electron Beam

The resolution of lithography techniques needs to be extended beyond their current limits to continue the trend of miniaturization and enable new applications. But what is the ultimate spatial resolution? It is known that single atoms can be imaged with a highly focused electron beam. Can single atoms also be written with an electron beam? We verify this with focused electron-beam-induced deposition (FEBID), a direct-write technique that has the current record for the smallest feature written by (electron) optical lithography. We show that the deposition of an organometallic precursor on graphene can be followed molecule-by-molecule with FEBID. The results show that mechanisms that are inherent to the process inhibit a further increase in control over the process. Hence, our results present the resolution limit of (electron) optical lithography techniques. The writing of isolated, subnanometer features with nanometer precision can be used, for instance, for the local modification of graphene and for catalysis

Molecule-by-Molecule Writing Using a Focused Electron Beam

The resolution of lithography techniques needs to be extended beyond their current limits to continue the trend of miniaturization and enable new applications. But what is the ultimate spatial resolution? It is known that single atoms can be imaged with a highly focused electron beam. Can single atoms also be written with an electron beam? We verify this with focused electron-beam-induced deposition (FEBID), a direct-write technique that has the current record for the smallest feature written by (electron) optical lithography. We show that the deposition of an organometallic precursor on graphene can be followed molecule-by-molecule with FEBID. The results show that mechanisms that are inherent to the process inhibit a further increase in control over the process. Hence, our results present the resolution limit of (electron) optical lithography techniques. The writing of isolated, subnanometer features with nanometer precision can be used, for instance, for the local modification of graphene and for catalysis

Role of NH₃ in the Electron-Induced Reactions of Adsorbed and Solid Cisplatin

The electron-induced decomposition of cisplatin (<i>cis</i>-Pt­(NH₃)₂Cl₂) was investigated to reveal if ammine (NH₃) ligands have a favorable effect on the purity of deposits produced from metal-containing precursor molecules by focused electron beam induced deposition (FEBID). Scanning electron microscopy showed that cisplatin particles of different sizes react violently during electron irradiation. In particular, faceted particles of a few μm in size started to boil, became spherical and subsequently degraded. Energy-dispersive X-ray spectroscopy gave evidence for the formation of nearly pure platinum and a decrease of the chlorine content. Nitrogen, however, was not detected, pointing to an efficient and rapid removal of NH₃. In contrast, PtCl₂ particles do not degrade under comparable conditions, demonstrating that the ammine ligand plays an important role in the reduction of cisplatin to pure platinum. The fast release of NH₃ ligands under electron exposure was confirmed by high resolution electron energy loss spectroscopy, focusing in particular on low-energy electrons as produced in high amounts during the FEBID process. Finally, FEBID experiments using cisplatin adsorbed from the gas phase onto a surface produced amorphous deposits. In contrast to the decomposed cisplatin particles, these deposits had a chlorine content of about 50 at. %. Only after extensive irradiation in a transmission electron microscope was this chlorine content reduced and were crystalline particles obtained. In conclusion, using NH₃ as ligand in metal containing FEBID precursors can favor the formation of pure metal deposits, but its effectiveness depends on the precise experimental conditions

Role of NH₃ in the Electron-Induced Reactions of Adsorbed and Solid Cisplatin

The electron-induced decomposition of cisplatin (<i>cis</i>-Pt­(NH₃)₂Cl₂) was investigated to reveal if ammine (NH₃) ligands have a favorable effect on the purity of deposits produced from metal-containing precursor molecules by focused electron beam induced deposition (FEBID). Scanning electron microscopy showed that cisplatin particles of different sizes react violently during electron irradiation. In particular, faceted particles of a few μm in size started to boil, became spherical and subsequently degraded. Energy-dispersive X-ray spectroscopy gave evidence for the formation of nearly pure platinum and a decrease of the chlorine content. Nitrogen, however, was not detected, pointing to an efficient and rapid removal of NH₃. In contrast, PtCl₂ particles do not degrade under comparable conditions, demonstrating that the ammine ligand plays an important role in the reduction of cisplatin to pure platinum. The fast release of NH₃ ligands under electron exposure was confirmed by high resolution electron energy loss spectroscopy, focusing in particular on low-energy electrons as produced in high amounts during the FEBID process. Finally, FEBID experiments using cisplatin adsorbed from the gas phase onto a surface produced amorphous deposits. In contrast to the decomposed cisplatin particles, these deposits had a chlorine content of about 50 at. %. Only after extensive irradiation in a transmission electron microscope was this chlorine content reduced and were crystalline particles obtained. In conclusion, using NH₃ as ligand in metal containing FEBID precursors can favor the formation of pure metal deposits, but its effectiveness depends on the precise experimental conditions

Selective Functionalization of Tailored Nanostructures

The controlled positioning of nanostructures with active molecular components is of importance throughout nanoscience and nanotechnology. We present a novel three-step method to produce nanostructures that are selectively decorated with functional molecules. We use fluorophores and nanoparticles to functionalize SiO features with defined shapes and with sizes ranging from micrometers to 25 nm. The method is called MACE-ID: molecular assembly controlled by electron-beam-induced deposition. In the first step, SiO nanostructures are written with focused electron-beam-induced deposition, a direct-writing technique. In the second step, the deposits are selectively silanized. In the final step, the silanes are functionalized with fluorescent dyes, polystyrene spheres, or gold nanoparticles. This recipe gives exciting new possibilities for combining the highly accurate control of top-down patterning (e-beam direct writing) with the rich variety of the bottom-up approach (self-assembly), leading to active or responsive surfaces. An important advantage of MACE-ID is that it can be used on substrates that already contain complex features, such as plasmonic structures, nanoantennas, and cavities