Many ALD researchers will recognise M. Pessa from early ALD publications. The first scientific article published in Finland on ALD in 1980 (Ahonen et al.) is co-authored by Pessa, and so is the review article in Journal of Applied Physics in 1986, which has been chosen to define the end year of VPHA. Both articles were featured and described in the recommended reading list of early ALD publications in the VPHA JVSTA focused review, http://dx.doi.org/10.1116/1.4971389 (open access).
Pessa has been further related to two puzzling questions which I have encountered during VPHA. I believe that both questions have received decent answers.
- When I started to work at VTT Technical Research Centre of Finland in 2004, I soon learned from a colleague who had worked at TUT that there is (/was?) an old ALD reactor displayed labelled as "the world's first ALE reactor". When I first heard this, I admit that I was very surprised. How could this be true? ALE was invented in Espoo by Suntola, after all.
- I have - of course - been curious of when the Finnish and Soviet ALD scientists first met. When during the past few years I presented the question to several long-term scientists in Finland who were active already in 1990, I got always basically the same answer: the first meeting was at the ALE-1 conference in 1990 in Helsinki, where these researchers "just appeared". How come they "just appeared" there?!? How did they find their way to the conference?
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| Copy of the cover of book of programme and abstracts, ALE-1 conference, Espoo/Helsinki, Finland, June 13-15, 1990. |
As for the first question, I believe that the answer has been found during the VPHA during the discussions with the Finnish inventor Tuomo Suntola. The world's oldest _existing_ ALE reactor may indeed well be located in Tampere. Suntola and co-workers of course built the first ALE reactor in Espoo, Finland in 1974. It was a rotary spatial ALD system, as described in the "ALE story" essay in CVD 2014. According to Suntola, this reactor no longer exists; it has long ago been discarded. The ALE story shortly tells also how ALE research in Tampere started soon after the original invention: thanks to Suntola's docentship at TUT, TUT was the first university lab to get involved in the ALE research in Finland. Reactor building has probably started in 1975 and if a reactor still exists, it should indeed be the world's oldest existing ALE reactor. Here is a copy of what is told in the ALE essay (http://dx.doi.org/10.1002/cvde.201402012) about ALE in Tampere:
"9.5 Early ALE in Tampere, FinlandAs for the second puzzling question, I found the answer in St. Petersburg when visiting the St. Petersburg ALD groups in November 2013 for the first time. I first met Prof. Drozd who came to meet me at the Findlyandskii train station (same place as where Drozd had welcomed Suntola in 1990). Prof. Drozd had learned of the coming ALE-1 conference from --- Markus Pessa. Pessa and Drozd both are semiconductor physicists. They had met each other at some electron physics (?) conference in Estonia (Tallinn), it must have been late 1989 or early in 1990. At this time, Drozd knew already of ALE works in Finland (see the ML essay in CVD 2015, http://dx.doi.org/10.1002/cvde.201502013). Pessa had told Drozd about the coming ALE-1 conference. Prof. Lauri Niinistö from Helsinki University of Technology (HUT), the chair of the conference, further helped Drozd as well as Aarik (from Tartu, Estonia) to participate. In his invited talk at Baltic ALD 2016 in St. Petersburg, Drozd told this story, similarly as he told me in November 2013 (travel report from Baltic ALD 2016 here).
In 1973, before Suntola had started the work leading to ALE and EL, he was invited to give lectures on semiconductor physics in Tampere University of Technology (TUT). Suntola was nominated as a docent in TUT, and he continued to give the lectures every second Friday for a couple of years. In 1975, after the early results in the EL project, Suntola encouraged the small TUT group to work on ALE of the group III-V semiconductors. The challenge was taken by M. Ahonen, who at that time was a graduate student. In 1978, Markus Pessa was nominated as the professor of physics in TUT. He took care of the lectures on semiconductor physics and directed a vital research activity on the group III-V materials, using the conventional MBE technology. Pessa's work led to effective GaAs laser technology and successful industrial activities in optoelectronics."
Prof. emeritus Markus Pessa, who has created a strong optoelectronics research centre and contributed to many start-ups in Tampere, has thus several times crossed paths with and influenced the ALD community, too.
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| First pages of the book of programme and abstracts, ALE-1 conference, Espoo/Helsinki, Finland, June 13-15, 1990, showing the names of persons in the organizing committee and scientific committee. |
UPDATES, Feb 15, 2017:
Details from Prof. Victor Drozd, Feb 13, 2017 (received per email):- We have met with M.Pessa in Tallinn university at fall workshop on MBE-MEE technology in 1989. It was the end of October. (MEE is a particular choice of MBE with sequential interrupting of beams – equal to ALE). I was there in Tallinn with my colleagues A.Romanichev and I.Nikiforova and J.Aarik from TU was there too. Markus <Pessa> told us about preparation of 1-st ALE in Helsinki and promised contact to L.Niinistö on a subject of our participation. That time great problem was currency exchange. Markus <Pessa> new about investigations on ML in Leningrad. Thanks for Lauri <Niinistö> he gave me and Jaan <Aarik> support for ALE-1.
Details from Prof. Jaan Aarik, Feb 14, 2017 (received per email)
- I really participated in this meeting in Tallinn. I do not remember when exacty the meeting was and whether Markus had/spread any information about ALE-1 during this meeting. I remember, however, that I had a rather long disscussion with Markus after this meeting and I also remember that he was leaving or had already left the ALD business.
- My idea to participate in ALE-1 was initiated by a leaflet that I received from my colleague Prof. Mart Elango. He had, in turn, received that during a surface science conference or during his visit to MAXlab synchrotron radiation center in Lund. Anyway, my participation in ALE1 became possible mainly because of Prof. Lauri Niinistö's support. After sending my abstract to the conference I wrote him as a chairman of the conference about our very limited budget (possibilities) for this kind of visits and he was so kind and organized a free accommodation for me in Helsinki.
- By the way, when I met Lauri first in Helsinki during ALE1, I was quite impressed because his first words to me were "Me võime rääkida eesti keeles", i.e. "We can talk in Estonian". It appeared that he had had long-time contacts with some other groups from Tallinn and Tartu, and because of that he could speak a very good Estonian and knew very well the situation in Estonia and in the whole Soviet Union.
- This is breafly the story about how I could join ALE1 symposium. However, the meeting with Markus Pessa in Tallinn was probably a reason why he invited me to join his group of optoelectronics at the Tampere University of Technology and at spin-off company Tutcore. This collaboration (in 1994-1999) was not related to ALD at all and was based on my earlier background in semiconductor physics and development of diode lasers and other optoelectronic devices. During my stay at TTK I also saw "the first ALE reactor" but I think (I do not remember exactly) that there was written "the first UHV ALE reactor" or "the first MBE-ALE reactor", which both are evidently right statements.
- Minor modification of Riikka's text, on the basis of the responses by Drozd and Aarik ("close to Tallinn(?)" --> Tallinn)
- Tallin corrected to Tallinn throughout
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Virtual Project on the History of ALD (VPHA) - in atmosphere of Openness, Respect, and Trust
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