Nanotechnology is one of the key innovative fields serving many essential branches like energy, healthcare, and consumer goods with new materials. One bottom-up strategy to design those materials with nanoscale precision is to compose them from molecular building blocks via self-assembly on solid surfaces or by on-surface (chemical) reaction in ultra-high vacuum (UHV). This procedure however is limited to thermo-stabile, sublimable molecules only, when deposited by the classical vapor deposition methods. Access to other, thermo-sensitive building blocks with fascinating functionalities like many organic compounds and complex biomolecules are highly desired as they exert exceptional electrical or optical properties when they assemble into 2- and 3-dimensional networks (OLEDs, spintronic elements). The potential of the plethora of these fragile molecules keeps however locked without a universal method capable to handle in particular delicate molecules under vacuum conditions without compromising their integrity.
By completing the SoftBeam project we could lay all the fundamentals for such groundbreaking and versatile platform. The underlying “Controlled Ion Beam Deposition - CIBD” technology derives from results obtained in the ERC MolArt project. In the scope of the ERC-PoC we were able to implement the principle in an innovative operative setup, to refine and systematically test all procedures, to figure out the points for further improvements, and to clarify suitability and requirements with field-test users and potential future customers, supplemented by an assessment of the relevant market figures.
In brief, the work flow at start consisting of an electrospray unit, two innovative types of ion guide and a deposition chamber was complemented with a new developed powerful digital quadrupole with sophisticated electronics and a third new invented ion guide. Efforts to miniaturize and precisely guide the ion beam resulted in a 10-fold increased resolution and vacuum transmission of 25%, an unrivalled recovery, rather low kinetic energies (currently down to 2eV) and strong reduction of gas burden. This combination allows for a nominally unlimited mass/charge range at an unrivalled mass resolution for a deposition system and a vacuum performance surpassing expectations.
Field tests conducted by researches and students on 4 different chemical classes covering species of a mass range of 4 logs up to 2 Mega-Daltons (proteins, DNA, tetra-pyrolles, de-novo synthesized organic compounds) revealed the flexibility of the system with respect to the kind of the species. Mass spectra and high-quality deposition results investigated by STM did prove an accurate handling of the species. The technical inventions have been filed for patent, experimental data are being prepared for publication in a peer-reviewed journal.
Conclusions and outlook: We demonstrated, that SoftBeam is a small-sized deposition system ideally suited for beam generation and deposition of solvable thermo-labile molecular species. It features a high ion flux, an excellent mass separation and a very low kinetic energy of the ions during deposition. User tests proved the system as robust and reliable. Feedback from experts and requests from potential customers clearly strengthened the view of a highly desirable, versatile platform in the field of nano-design and UHV-analytics. Hence the CIBD fulfills most technical and application prerequisites to become a useful and essential element for future exploration, fabrication and analysis of novel organic-based nanotech materials. However, in order to reach maturation level for marketing few gaps are yet to be filled: While the already great ion guide performance may be improvable in incremental steps only, the system is run with quite basic spraying equipment to date. This opens much room for additional optimizations to improve ion flux and recovery. We analyzed the deposition results by a STM flange-mounted. In the course of our studies we realized that direct access to a broad spectrum of analytical systems covering various STM including those with low temperature settings, AFM, XPS and even TEM would be highly beneficial to attract a greater community. It becomes crucial to develop an interchangeable interface to flexibly connect the CIBD system to any suitable standard analysis device.
