In memory of Volker Lehmann (10 December 1956 to 26 May 2006)
Authors: Föll H. , Gösele U. 
Published: May 2007

Volker Lehmann was born in December 1956 in Ulm, South Germany. After his family moved to Viersen in Middle Germany and he finished secondary school, he studied Electrical Engineering at the RWTH Aachen, one of the foremost German engineering universities. His chosen study course required internships in industry, and by one of those chains of events that seem to contain random elements, he appeared one day in 1981 in the freshly formed “solar” department of Siemens Central Research in Munich, where he met one of us (H.F.) for the first time. Siemens had started a program to produce silicon by various novel ways. Urgently needed was a “quick and dirty” way for assessing the potential of irregular shaped pieces of Lab‐produced Si for solar cell production. An electrochemical system with the ability to extract the photocurrent via a solid–liquid junction was the method of choice, and Volker Lehmann was starting his first experiments in this line of work.

He proved to be extremely capable. Not only did he master the necessary background in Si materials science in a short time, but his training as an engineer in conjunction with his strong background in building complex machinery from various pieces of debris found in any lab, quickly earned him the unofficial position as the lab engineer.

This first encounter of Volker Lehmann with Si electrochemistry proved to be decisive for his future career. His internship was followed by work for his diploma thesis (entitled “Characterization of Solar Silicon by Electrochemical Measurements Employing Semiconductor–Electrolyte Contacts”); work that produced his first publication with the title: “A high‐speed characterization technique for solar silicon”.

After an interruption necessitated by civil service in lieu of military service, PhD work followed – but only after his application to the Munich School of Arts was turned down. Volker Lehmann was not only an outstanding scientist but also a talented and dedicated artist, and throughout his career he was actively producing art – pictures, lithographies, sculptures and, particularly remarkable, “perpetuum mobiles” embodying both artful work and tricky engineering – it took us longer and longer to figure out where the battery was hidden. In his art, found in many homes and offices, he will live on just as much as in his scientific contributions.

What was the loss to the artists' community has been the gain for materials science: Volker Lehmann abandoned the prospect of a career in the arts and in 1985 started PhD work in Materials Science, supervised by one of us (H.F.) in the Siemens laboratories, and formally connected to the University of Erlangen in Bavaria. His thesis was finished in 1988.

What has started as employing the Si–electrolyte junction for immediate uses quickly blossomed into work driven by scientific curiosity, only mildly tempered by possible applications. Results of ingenious experiments quickly lead to the discovery of the “ELYMAT” principle for lifetime mapping in Si and the experimental discovery (after it had been predicted) of macropores in n‐type Si under backside illumination. A long series of publications and of patents resulted form his work, establishing him early on as leading researcher in our common field.

Meanwhile, one of the authors (U.G.) had joined Siemens for a brief period, and left for a professorship at Duke University in North Carolina. Volker Lehmann got a one year postdoc scholarship and joined Duke University even though Siemens Corporation had offered him a “real job” in Munich. His main job as a postdoc was to work on silicon wafer bonding, but his heart was still mainly in the electrochemistry of silicon. His substantial background knowledge concerning microporous Si resulting from many experiments that Volker Lehmann had done but never published, met the concept of quantum wires, and things suddenly started to make sense. His now highly cited Applied Phyics Letters publication on this topic appeared practically at the same time as Canham's seminal contribution and finally and firmly established him in the porous Si community. At Duke University the idea was conceived that Volker Lehmann should write a book on the “Electrochemistry of Silicon” which many years later he actually did.

When he came back to Siemens in 1989, he joined the research arm of the semiconductor branch where he remained to the end – even after Siemens branched off Infineon, and Infineon (quite recently) Qimonda. It is remarkable and reflects his passionate interest for science that for all this time he managed to convince his management that work on the electrochemistry of Si was important and should be funded. First class work, spanning the range from fundamental investigation, e.g. to current and voltage oscillations at the Si electrode, to revenue generating products like “bio‐chips”, made him a coveted speaker at conferences. In this capacity he has substantially contributed to all PSST's – from the first one in Mallorca 1998, to the most recent one in Barcelona 2006. As many will remember, an unexpected illness forced him to abandon the Barcelona conference; these proceedings nevertheless contain his last contribution to the field.

Volker Lehmann was not only an outstanding scientist and artist, he was also a person with an extraordinary vitality; radiating good cheer and making friends as he walked along. He was clearly enjoying live. He was always open and helpful, and often the ringleader for extracurricular activities. Many will remember him, for example, as the guy who organized and led the hikes in Tenerife, prodded reluctant youngsters into an early swimming in the (still cold) ocean or as the “bar keeper” in Cullera, who served the beer still needed by some of us after the official bar keeper had retired.

Volker Lehmann died unexpectedly and tragically on 26 May 2006. He was married for 16 years and leaves a wife and two sons.

He has enriched our professional and private lives. He will be missed and remembered.