Mikko Ritala belongs to the most elite level in chemistry in Finland, ranking among the most cited chemists in the country, states the Magnus Ehrnrooth Foundation, an organisation that promotes scientific research in mathematical fields, in its award justification. In recent years, Professor Ritala has been particularly active in developing novel nanostructured materials by employing the method of atomic layer deposition (ALD). The award, worth €20,000, was granted on 29 April 2020, but the ceremony organised by the Finnish Society of Sciences and Letters will be postponed to the autumn.
Another award was bestowed earlier in the year, as Mikko Ritala was granted the ALD 2020 Innovator Award “For Original Work and Leadership in ALD”, a distinguished recognition awarded by the international ALD researcher community.
Ritala, who has been serving as professor of inorganic materials chemistry at the University of Helsinki from 2003, was born in Nokia and currently lives in Espoo. Most of the time he commutes to Kumpula Campus by bicycle. Ritala has played basketball on all league levels, currently representing the team Leppävaaran Pyrintö Faijat in the fourth division. The season interrupted by the corona virus was already 43rd in a row.
A series of breakthrough discoveries
Ritala has no single achievement in his research career that he considers more important than any other. The development of atomic layer deposition at the University of Helsinki, now ongoing for 30 years, constitutes a series of discoveries, all of which have required a chemistry of their own. After developing a certain type of film to meet the needs of the semiconductor industry and successfully determining proper chemistry for the process, that film has been exploited in a range of other applications as well.
Noble metal processes have also been discovered in stages, in the end also realising the alchemist’s dream, the ALD process for gold.
On the one hand, research focused on ALD processes has been basic in nature. On the other, it has directly responded to the needs of the industry and the challenges brought about by those needs. These needs have been heeded particularly closely in the Chemicum building at the University of Helsinki, through ASM Microchemistry Oy, an international company working under the same roof.
“In ALD chemistry, processes are developed in a fairly simple manner through practical experimentation. You look for the right precursors and conditions to be tried out for repeatedly manufacturing proper thin films. An ALD reactor is like a black box into which you feed the precursors, after which you choose the parameters and hope for a high-quality film as the final product,” Ritala says. The processes taking place in the reactor are studied by analysing the film coming out of the reactor, after which the settings are fine-tuned for the next experiment.
When the film produced is good and qualifies useable, the underlying process is usually taken directly to product development by businesses. At some point, researchers may lose visibility to how the process is being exploited. Apparently, this does not bother scientists involved in ALD, as they are focused on discovering more and more new materials and applications.
Another aim of the researchers is to advance the knowledge pertaining to surface reaction mechanisms during ALD processes. For this research, new equipment is expected early next year, thanks to profile building funding awarded by the Academy of Finland. As knowledge of reaction mechanisms increases, new precursors and processes can be developed, as well as new fields of application based on them.
The fabrication of coatings that boost the growth of bone cells, for example, on the surface of implants, is an interesting and distinct area of research. Such coatings could in their composition mimic the minerals found in bones, or produce the desired biological response in another way.
What do toothpaste and ALD thin-films have in common?
A characteristic of atomic layer deposition is that the process can be used to manufacture extremely thin films, precisely uniform in thickness, that adhere accurately to the contours of the object being coated.
Are these films everlasting or is there a risk of engendering a problem resembling that of microplastics?
Mikko Ritala posits that, as a rule, the films are stable and securely attached to the surfaces they cover, but certain films are more reactive than others, potentially at some point reacting with air, or oxidising. Were a coating to come off from the surface it is covering, it could end up in the environment, which of course makes relevant which substances are used to produce the films. Titanium oxide, used as a pigment in foodstuff and toothpaste, is among the earliest ALD thin film materials.
In the research he conducted for his doctoral dissertation in 1992, Ritala deposited titanium oxide films, which, as he recently noted, have remained undamaged and intact to this day.
A Centre of Excellence in atomic layer deposition
The ALD laboratory, which was nominated as an Academy of Finland Centre of Excellence for 2012–2017, was born out of collaboration between Mikko Ritala and Markku Leskelä.
“Both of us were needed to build up a critical mass,” says Ritala, who has been heading the research group now for a couple of years. Leskelä, now retired, continues to work at the University of Helsinki almost daily.
The collaboration of Ritala and Leskelä has its origins in Turku where Ritala began studying chemistry at the University of Turku, graduating with a master’s degree in 1991. During that time, Leskelä worked as a professor at the same institution. After graduation, Ritala transferred to pursue doctoral studies at the University of Helsinki, where Leskelä had established an ALD laboratory.
Today, the laboratory employs some 20 scientists, including doctoral students from Iran, China and other countries. “This is cooperation at its best. No one will succeed by themselves,” Ritala praises the group as well as their other partners, the closest and longest-lasting of which operates at Kumpula Campus. “From the start, the ion beam techniques of the Accelerator Laboratory of the Department of Physics have played an important part in our ALD research.”
Graduates have quickly found work in companies involved in the field, a number of which can be found in Finland. Why has Ritala remained at the University?
“A certain independence and the opportunity to innovate are what’s best about the academic world,” Ritala says. Another factor that has kept Mikko Ritala at the University of Helsinki is the freedom to organise his work, which has also helped him to resist the siren song, as he himself describes the job offers that have come his way from the industry.
Ritala has kept a close eye on business operations, and he is responsible particularly for the marketing activities of the Kumpula Business Labs, which provides facilities and research cooperation opportunities between businesses and the University.
“At the moment, all of the Kumpula Business Lab facilities are in use, and we are in fact steering interested parties to other University facilities,” Ritala notes.
Relief for climate anxiety
“Chemists are producing solutions to mitigate climate change,” Mikko Ritala points out. Measuring and talking politics is not enough – sustainable development and the realisation of circular economy requires chemistry.
In recent years, chemistry has not been a popular field, which means that prospective students have found it easier to get admitted to than many other disciplines. This year, there were 400 applicants against 100 available places, with most of the admissions based on certificates.
Ritala recommends studying chemistry to young people suffering from climate anxiety, welcoming all motivated individuals.