Who was Jan Czochralski? Out of the shadows

For those working in the field of crystal growth, the name Czochralski is well known as a particular technique, the Czochralski method, whereby a large pure crystal can be pulled from a molten substance. This is the standard method, for instance, for growing huge crystals of silicon and germanium, as well as many other crystalline materials of interest. The importance of the Czochralski method can, therefore, not be overstated as so much of the modern world depends on being able to grow Si/Ge crystals on an industrial scale.

But who was Czochralski and what did he actually do? His story is interesting and mysterious, the stuff of movies. It is a story of discovery and tragedy set against the events in Poland and Germany in the 1930s and 40s. The following account of his life has been adapted from a lecture I gave a few years ago in Kraków, Poland. The book Jan Czochralski Restored by Paweł Tomaszewski (2013) provides much more detail than is possible in this short article. I shall try to highlight the significant events of his life here, a story that is now well known in his country of origin, Poland, but somewhat overlooked elsewhere.

Early Life and Career

Jan Czochralski was born in 1885 (Fig. 1) in a small town called Kcynia (Exin in German) near the Polish city of Poznań. At the time, this part of present-day Poland was in the Prussian partition (from 1772 to 1795 Poland had been partitioned between Prussia, Austria and Russia, only regaining its independence in 1918). So officially, Czochralski was a citizen of Germany. The question of his 'Polishness' became an important matter for him many years later, as we shall see.

It seems that little is known about Jan's early years or his time at school. Curiously, no evidence has been found of him gaining the so-called 'matura', the expected qualification needed for university studies in Poland. It is known that Jan travelled to Berlin (Fig. 2), where he worked from 1907 to 1917 at the Kabelwerk Oberspree cable factory (AEG), as an assistant to the German engineer Wichard von Moellendorff. During this time, he worked on introducing aluminium into electrotechnology. But it was here that he made a momentous discovery. The story behind this is legendary and there are several versions of it. But it goes something like this.

Discoveries

It was 1916, during World War I. One more working day was coming to a close and the laboratory had emptied. Jan was sitting at a table to complete the researcher's routine: writing down the results of the day's work. He was tired and preoccupied; for weeks, he had been searching for a way to measure the crystallizing speed of metallic alloys. The war restrictions on material supply were being felt more and more painfully. So the industry was urgently in need of some substitute materials, such as metal alloys, which could replace the traditional ones used until then.

Probably from being tired, Jan absent-mindedly dipped his pen into a pot of molten tin that was cooling off, thinking it was the ink well. He noticed a thin thread of metal hanging off the pen. Quite preoccupied, he changed the nib, putting a new one in, and carefully immersed the pen into the melting pot. Then he slowly pulled it out, and once again, he saw a hanging thread. He continued with another nib. The same thing happened. So he took one more nib. It was just the same. Having broken off the metal thread, he dipped the pen again in the melted tin. This time he pulled it out briskly: the thread was not there. Interesting….

Jan failed to notice that the sun had long stopped peeping into the lab through the windows. He was so absorbed 'playing with' the tin thread, pulling it out of the melting pot. Could it be so that the length of the thread depended on the speed with which he pulled the pen out? 'So I've found a solution' he thought. Could that be some property of the metal?

A series of prompt, yet systematic, experiments demonstrated that the quicker he pulled the pen out, the shorter the thread was. Jan swiftly wrote this observation down so as not to forget this interesting relationship. He spent the following days working out a device that would help to more objectively test whether his accidental observation implied information about the material's properties (Fig. 3). He knew from Gustave Tammann's¹ previous studies that crystallization occurred in a small hole of a thin glass tube. The incision on the nib of his pen served like such an open capillary. The hand had to be substituted by a mechanism to lift the tube at a chosen fixed speed. At first, he used a clockwork motor (Fig. 4).

The news of Czochralski's discovery² travelled fast among his colleagues. It must have been an important one as they could not have read about it by then, as the first scientific information was printed only in 1918. Soon one more benefit of the crystallization speed measurement method was observed: the acquired metal thread was a single metal crystal. This provided the opportunity so many scientists had been dreaming of as they were aware that testing many metal physical properties was possible only on single crystals. Several years before, W. H. Bragg and his son W. L. Bragg had demonstrated that a monocrystalline solid is built of atoms arranged in an almost perfect way. Yet, prior to Czochralski's discovery, a method of obtaining metal crystals simply and cheaply was unavailable. Thus, metallurgists were given an excellent tool for producing such materials, namely the Czochralski method. Interestingly, he did not patent the technology nor benefit financially from it. He may not have realized at the time the importance of this method, as it was other scientists later on who noticed that it could be used to grow large crystals.

In particular, it was Gordon Teal working at Bell Labs in the 1950s who modified Czochralski's method to grow large crystals of silicon and germanium for the first time. The 1955 patent (Fig. 5) by Little and Teal does not mention Czochralski's name but starts with the statement: "This invention is related to an improved method and apparatus for producing single crystals, particularly of germanium." Despite this, it is Czochralski’s name that is universally used to refer to this method of crystal growth. In addition to the growth of silicon and germanium, the Czochralski method is the leading technique for growing many other crystalline materials of interest, such as high-quality bulk oxide crystals. Whereas many semiconductors are now grown by epitaxy, there is still a need for high-quality oxide crystalline substrates.³

In 1917, Czochralski moved with his family (Fig. 6) to Metallbank u. Metallurgische Gesellschaft A.G. in Frankfurt am Main to found a new large laboratory, one of the best-equipped laboratories then in Germany. Here he invented a new metallic alloy called B-metal (German: Bahnmetall) used to make high-quality elements of bearings for the railway industry. It was cheap, very durable, and, most importantly, did not contain tin, which was expensive and hard to get at the time. By 1928 he was now famous and wealthy thanks to his income from this patent.

Another invention during this time is intriguing. In 1925, he built a device that he called a radio microscope (Fig. 7). It had already been discovered in the 1870s that the contact of a metal with a semiconductor displays rectifying properties. This allowed one to build semiconductor elements, so-called 'crystals'. Czochralski's idea was based on the old crystal radio sets where a needle was moved across a crystal to maximize the received radio signal. In his device, he scanned a copper needle across a polished aluminium wafer containing silicon inclusions. The radio microscope included an antenna to pick up a radio broadcast (later when working in Poland, he tuned it to the Polish radio station Raszyn). Whenever the needle met a silicon point, because of rectification, there was a change in the intensity of the radio signal. These points were then plotted to produce a map of the inclusions. This is the description in Czochralski's own words:

"Thus, if on the one hand, you connect the antenna with the alloy, while on the other silicon crystals are touched with a sharp needle connected with the phones, thus making the current flow through the phone's coil to the ground, such a system should affect the course of electromagnetic waves like every detector. What can be seen in the scheme is: any antenna whose current flows to the metal detector table serving as the sample base and to the microscope placed on the table. The researcher's needle, also metal, is joined with the phones' clips by means of an appropriate conductor. A rectified antenna current flows further on through the coils to the ground. When the needle touches a silicon crystal, once the electromagnetic waves reach the antenna, a sound is heard in the phones. (...) One can easily make the receiver in such a way that it is tuned merely to a particular wavelength (all we need thus is an induction coil of variable self-induction to be added into the oscillating circuit as marked in the sketch with the dotted line and the circuit tunes to a given wavelength) (...)".

Now, where have we seen a similar idea that many years later gave rise to a Nobel Prize?

Another area of research was recrystallization methods. For instance, he discovered that when annealed metal strips are stretched slightly at an appropriate temperature, recrystallization is induced, with crystals many centimetres thick and relatively free from crystallographic defects. In 1923 he was the first to publish in Poland an X-ray diffraction study of a single crystal and was soon demonstrating crystal structure models to visitors.

Poland

After all his successes in Germany, the story then takes a twist, which would later turn out to be cataclysmic. In 1928 he went with his family to Warsaw at the personal invitation of the President of Poland, Professor Ignacy Mościcki, himself an outstanding chemist. Czochralski later said: "I was tempted to return to Poland, (…) as my children were growing up and I wanted to send them to a Polish school so as not to let them become Germanized!" (Fig. 8).

In 1929, Czochralski was appointed Professor at the Faculty of Chemistry of the Warsaw University of Technology (Fig. 9) and was one of the first to be conferred with the University's honorary degrees. This was despite not having the usual formal qualification of the Polish matura, something that caused some in the University to look askance. At the University, he set up his own Institute of Metallurgy and Metal Science (Fig. 10) with significant state funding and a large number of staff. By all accounts, his institute was self-contained and seemed to act independently from the rest of the university. Unsurprisingly, this must have led to considerable jealousy among certain members of the University Faculties.

In the period 1934–1938, Czochralski became embroiled in a series of court battles, such as when he was accused of defamation by the metallurgist Professor Witold Broniewski and accused about the usefulness of B-metal (Broniewski argued that its use would cause the stoppage of railway transportation). Generally, these cases had their origin over the question of Czochralski's lack of official qualifications and questions about his citizenship (was he German or Polish?) and patriotism to Poland. Eventually, the courts found in Czochralski's favour. On 19 October 1936, Broniewski was sentenced by the District Court in Warsaw to a two-month suspended arrest and a fine of 500 złotys in a defamation trial brought by Czochralski. In December 1938, the Supreme Court upheld the above judgments.

At the institute over a period of years from 1930 onwards, much new equipment and facilities were added, some for research into materials for military armaments and some for civilian use. In May 1939, shortly before the German invasion of Poland in September, the physicist and later Nobel Laureate Professor Walther Gerlach (1889–1979) from Munich judged Czochralski's institute to be better equipped than many German institutions of its kind, despite having been shown merely its civilian part. A report to the Nazi Party Unit NSDAP, Berlin:

"In April, I received an invitation from the Director of the Institute of Metal Sciences of the Warsaw University of Technology, Professor Czochralski, additionally inviting me to stay in his house. I have known Professor Czochralski for 20 years; we were on especially friendly terms at the time when he headed the research laboratory of Metallgesellschaft in Frankfurt, and I was working at the University there. We cooperated a lot and have remained friends since. Despite being away, Professor Czochralski came briefly to Warsaw (…).

I had the opportunity to visit the Metal Science Institute of the Warsaw University of Technology only partially. Some of its sections are closed to visitors, as they are controlled by the army, since, like in many German institutes there too, Polish professors are working on the issues of state importance. What I saw in the Institute ranks among the most beautiful things I had ever seen, and which in Germany can only be found in industry research institutes. The Institute is housed in a large several-storeyed building raised for the purpose some years ago. It contains all the possible devices for experiments and auxiliary means for pure metal science, metal chemistry, metal physics and metal technology (working). It seems to me that it is mainly a research institution, but it is also involved in teaching; for teaching purposes, it has first-class aids and devices. I cannot tell the actual size of the Institute, yet I assess that it is four times as big as the new KWC Institute of Professor Debye in Dahlem. It seems likely that the (Warsaw) Institute enjoys substantial financing. Its studies are published in its own publications having some hundred pages annually. All the studies are almost exclusively written in Polish, with extensive abstracts in German, English or French.

In my judgment, the Institute focuses on strictly academic issues: alloys, steel hardening, light metal improvement: also some scientific-technological issues: investigating metals, corrosion, etc. There also must be some target-specific research carried out. Apart from specialized research apparatuses, I have also been shown apparatuses for series tests on a large scale.

(…) In brief, I can say that despite the political tensions, the trip went on undisturbed (…) Politics was entirely excluded from our talks; all we did was express the desire that this visit could be followed by further scholarly contacts."

World War II

A result of Gerlach's report was that it helped the occupying forces in the destruction of the laboratories, as they knew what equipment and facilities existed. Under German occupation, all high schools and universities were closed down, yet Czochralski was able to set up a new technical laboratory using the Institute's equipment and people.

From time to time, senior Nazi officials were seen to visit him, e.g. on 4 November 1939 the Institute was visited by SSHauptsturmführer Professor Heinrich Harmjanz of Einsatzkommando⁴ IV der Sicherheitspolitzei Warschau, who reported:

"It is a huge Institute equipped with the most modern apparatus and was financed mainly by the research resources of commissions placed by Polish industry. It employed 85 paid employees and assistants. The head, with fluent German, worked for some dozen years in German industry and personally became acquainted with many German plants. He informed me that, until the outbreak of the war, he had maintained wide contacts with German industrial plants. He told me that he had already expressed to Dr Fischer, head of the Warsaw District civil administration, his readiness to cooperate with the Hermann Göring State Works. Apparently, Dr Fischer considers the possibility of using the Institute for a four years' plan of Poland's economic recovery as worth analyzing."

The activities of Czochralski during this period were complicated. They have been fully documented by Tomaszewski and will not be described here.

During German occupation of Warsaw, ever more restrictions on daily life were imposed on the population. Despite this, Czochralski apparently continued to live a lavish life in his villa, where he held receptions and collected artworks. The Jewish population of Warsaw was moved into a confined area of the city, the so-called ghetto. Many died of starvation and disease or were sent to the death camps. Finally, on 19 April 1943, an uprising began by the remaining ghetto population. Although being poorly equipped and small in number, the Jewish resistance was able to hold out until the final defeat on 16 May, followed by the wholesale destruction of the ghetto area. The following year from 1 August until 2 October, the Warsaw Uprising took place, which resulted in massive destruction of the city.

It is known that, in early September 1944, Jan lived in Milanówek (just outside Warsaw). After the Warsaw Uprising, the Nazis ordered the transportation of the property of the blockaded and ruined city. Czochralski, as the head of the Materials Research Unit, was also involved, on the German authorities' instruction, in transporting precious apparatus of the Institute. As a rule, people deviated from the marked route to save something from their own or a friend's flat. The latter, however, was not always possible (when the transport was accompanied by a German soldier), or was not necessarily safe if the Nazis were to find among the possessions something outside the pass list. Very often, the evacuation was a paid procedure: most likely, money was paid to the transporting team and bribes were paid to the guards controlling the vehicles leaving Warsaw.

Ignominy

On 7 April 1945, after the Germans had left, Czochralski's tragedy began. On that day, the Prosecutor of the Special Criminal Court for the Court of Appeal in Warsaw announced the arrest of "a certain Jan alias Johann Czochralski, a citizen of the Reich, former honorary Professor at the Warsaw University of Technology, who after the Warsaw Uprising was supposedly dwelling in Piotrków." This was in compliance with the so-called August Decree, namely the Decree of the Polish Committee of National Liberation of 31 August 1944 "on the Sentence for Nazi Criminals Guilty of Assassination and Torturing Civilians as well as War Prisoners and for Traitors of the Polish Nation." Several people spoke up for him, where one of the issues considered was whether he was a Pole or German. This was a complicated matter⁵, as he constantly maintained his Polish identity despite having been born under Prussian rule. Fortunately, the investigation proved that Czochralski's activity during the occupation did not show symptoms of collaboration with the Nazis and therefore could not be classified as a "betrayal of the Polish nation." Such was the Prosecutor's conclusion, and so the investigation was dismissed for lack of evidence. He was released from prison on 14 August 1945.

At the Warsaw University of Technology, members of the Senate declared "as of the end of 1939 Dr Jan Czochralski ceased being considered by the Professors' body of the Warsaw University of Technology as a Professor of the Warsaw University of Technology and decides to respond that J. Czochralski's intention to work for the University of Technology is not valid". Thus Czochralski's name was erased from the list of Professors. Czochralski took the Senate's decision as his personal failure and humiliation. Despite having been proposed to emigrate to Austria and take a chair in Vienna, he and his wife returned to Kcynia. There he founded a small company BION producing health products, cosmetics and household chemicals. The rest of his life was doomed to infamy and oblivion. He died from heart failure on 22 April 1953.

The actual circumstances that led to the death of Czochralski at the age of 67 remain unclear. According to one version, it came as the result of the intrusion of officers of the infamous 'U.B.', Secret Police, searching, in compliance with some denunciation, hidden dollars from the sale of his house in Warsaw. However, they were unable to find anything. Terrified at the vision of wreckage of his house, Czochralski revealed to them an ingenious hiding place in a window ledge. His 20-dollar golden coins were thus lost, and the price for that was highly paid: a heart attack. According to a second version, the heart attack happened later: it was supposed to have occurred after chasing some boys vandalizing his garden. His grave remained nameless for 45 years. Even here, mystery is attached to Czochralski’s life.

The secret

So, this is how the Czochralski story remained during the long years of the Communist government in Poland. During this time, mention of his name was actively discouraged. It was clearly of great sensitivity to the then Polish authorities. However, some academics, including Tomaszewski from the Polish Academy of Sciences in Wrocław (before the war Breslau), began to investigate Czochralski's history. I recall that at the European Crystallography Meeting in 1986 held in Wrocław, Tomaszewski wanted to hold an exhibition on Czochralski's works and to invite a Czochralski expert to give a plenary lecture at the opening of the conference. However, mention of Czochralski was still a sensitive matter, and after receipt of various telephone threats, the lecture was given quietly in a rather nervous and tense atmosphere late one afternoon. But in 1989, the Communist government fell and a fully democratic government took power. Suddenly, under the new President, Lech Wałęsa, it became possible to talk openly about Czochralski, and, importantly, to discover more of his life from secret archives.

Subsequently, the following are some of the discoveries:

• In 1941 the Germans demanded Czochralski's help to provide materials and equipment for their war effort. In fact, the demands for weapons were never actually fulfilled. He claimed that his Unit was overloaded with work.
• There is evidence of underground activity. Czochralski was given authority to provide employment certificates, and he gave many such permits to fictitious employees who were members of the Home Army.
• Together with his daughter, he was able to use his influence with the German authorities to intervene to release some people from concentration and POW camps.
• There is evidence of the manufacturing of arms for the Home Army (e.g. grenade shells).
• There is evidence that he sheltered two Jewish women in his home until the Warsaw Uprising.
• The German authorities managed to import a vital piece of American equipment with the help of the Swedes. When the apparatus finally arrived, Czochralski used a hammer to smash its essential component without which it could not operate.
• There is some evidence that Czochralski was instrumental in financially helping a previously owned Jewish business in the ghetto.

Czochralski recalled: "During the occupation, I lived in Warsaw in my own villa of 16 rooms at 4 Nabielaka Street. I lived there only with my family made up of 6 individuals; apart from us there lived 2 Jewish women who stayed with us until the Uprising. In total, there were 10 individuals living there. On several occasions the Nazis wanted to occupy the villa, which they eventually failed to do. I suppose that my name being well known in science accounts for it."

Interestingly, a photograph (Fig. 11) has been found of Czochralski attending the burial of an insurgent in the grounds of the Warsaw University of Technology. Incidentally, a few years ago, during a visit to the University for a meeting of the European Materials Research Society (EMRS), I was able to take a photograph (Fig. 12), which I think is at the same spot.

There remain other questions that have never been answered. Intriguingly, one has to ask why did President Mościcki invite Czochralski to Warsaw in 1928 and why was he, despite lacking the matura, made a Professor and given his own institute with full funding? Could it be that he was working all along for the Polish secret service?

Anyway, the result of all this is that, after much discussion, Czochralski's name was fully rehabilitated. On 7 September 2011, at the Congress of Physicists in Lublin, delegates of the Polish Physical Society adopted a resolution to appeal to the Polish Parliament to make 2013 the Year of Czochralski, as that year would be 60 years since he passed away. After some discussion, the Parliament declared 2013 as the Year of Jan Czochralski. The Senate of the University voted to restore his name to the list of Professors, and now each Fall meeting of the EMRS includes the presentation of a gold Czochralski medal (Fig. 13) to a distinguished materials scientist. Today, Czochralski is regarded as a national hero (Fig. 14) and he has finally emerged from the shadows. I understand that this year, Polish television will be screening a film about his life and achievements.

In 2003, the then President of Poland, Aleksander Kwaśniewski, stated:

"During the tragic times of the Nazi occupation, he demonstrated great courage and righteousness. He was involved with the Polish underground, he supported the fighters of the Warsaw Ghetto, and participated in the efforts to save museum collections of national culture. It is for this attitude that, following WWII, he suffered unfair accusations, which, though ungrounded, made it impossible for him to work at University. He was an individual of exceptional merits. A noble patriot, a devoted son of his Homeland."

With especial gratitude to Dr Paweł Tomaszewski, Institute of Low Temperature and Structure Research of the Polish Academy of Sciences in Wrocław, whose untiring perseverance to uncover the truth about Czochralski, sometimes under difficult circumstances, finally paid off!

References

Moellendorf, W. von (1911). Kupfer un Elektrizitaentindustrie. AEG-Zeitung, 13, 6.

Tomaszewski, P. (2013). Jan Czochralski Restored. Warsaw: Atut.