In recent years the industry related to computers and the internet has become a larger part of the economy and everyday life of humans. The computational parts are found in smartphones, cars, bank terminals, TVs, coffee machines and toasters. The smaller the structure, the more energy efficient it can be, the faster it can compute, the more integrated it can get.
Light sources
The smallest feature size is related to the light source used. One can get beyond the Rayleigh limit with multi-pattern, phase corrected images etc. But eventually one needs a shorter wavelength. The limit of DUV (deep ultra violet 193nm) was long known. Since the 1990s serious investigations have been made to go beyond. Eventually EUV (extreme ultra violet 13.5nm) emerged as the solution, and in 2026 the company ASML is the sole provider of light sources with this wavelength for large scale lithography to produce semiconductors. A “simple machine” costs easily 180,000,000 USD like the TWINSCAN NXE:3300B that first shipped 2013.
And the high-NA rather approach 400 million USD. My AR65 machine 6 years earlier at the Humboldt university in Berlin was not that expensive. Here at BESSY:
But I wondered what wavelength I was using to investigate my CdHgTe crystals. In the early 2000s we labeled our light as VUV (vacuum ultra violet) because for the energy used there is no window material available (6.2 to 124 eV, see my diploma thesis from 2008, page 19). We measured the energy in eV because the energy itself was more important. The conversion is easy:
where:
(speed of light).
(Planck’s constant),
With the Bessy Syncrotron I used the beam energy up to 125 eV, the respective wavelength is is actually shorter than the 13.5 nm (92 eV) used by ASML
But for most cases I needed less energy, the lower energy bands were more important for the optical and electronical properties of my narrow-gap semiconductor. Most measurements were actually done with the He I α line at 21.218 eV or 58.43 nm. That is significanly shorter than DUV, the shortest wavelength currently used for lithography in China with the Argon fluoride excimer laser ArF and 193 nm (6.42 eV). With immersion scanners (ArFi) one can achieve a high numerical aperture up to 1.35 and produce chips at nominal 7 nm. A great example of engineering achievements.
Our course is studying the Vietnamese language and culture. Both are strongly influenced by the Chinese neighbor and its language(s) and culture(s). With 4 Chinese students in our group it was fitting to visit the anual Lễ Hội Ẩm Thực Triều Châu (Teochew Food Festival, celebrated from the 16th to the 27th day of the First Lunar Month – March 4 to March 15, 2026) at the Hội Quán Nghĩa An (Nghĩa An Assembly Hall). There is so much to learn about culture and history here!
I could start with the background, since it looks very much like a temple. And a part of this Hội Quán (會館 – community hub) serves as temple, but also as a town hall, a mutual aid society, a commercial network hub, and a place of ancestral worship for immigrants adapting to life in Vietnam.
The specific Chinese group settled here are from Chaozhou (Chinese: 潮州, alternatively Chiuchow, Chaochow or Teochew) in the Teoswa region of east Guangdong, China.
The Food Festival
This festival has it’s own Wikipedia page, but currently only in Vietnamese: Hội quán Nghĩa An. As mentioned above it is held at the end of the first lunar month. It is famous for …
And we tried even more food:
One memorable part is.
Cultural importance
This community hall and the food festival were considered important enough for the Vietnamese culture that it got official recognition and protection. Here is a plate inside the community hall:
The text reads “DI SẢN VĂN HÓA PHI VÂT THỂ QUỐC GIA TẬP QUÁN XÃ HỘI VÀ TÍN NGƯỠNG TẾT NGUYÊN TIÊU CỦA NGƯỜI HOA TP. HCM” which translates to “National Intangible Cultural Heritage: Social Customs and Beliefs of the Lantern Festival (Tết Nguyên Tiêu) of the Chinese Community in Ho Chi Minh City”.
Here is an official list of such recognitions in Vietnam, starting 2012 and now having already 485 entrances: Danh mục Di sản văn hóa phi vật thể quốc gia (List of National Intangible Cultural Heritage).
Since May 16th, 2024, I try to study at the Su Pham university. The requirement in 2024 was to have at least 15 students to get this course started, even though it was intended for 20 students. By June 17th I had submitted my application, but still had to wait for a response in September, when the new semester starts
September 2024 – not enough students
After Independence Day of Vietnam (September 2nd) I finally got an answer on September 5th: We are only 7 students, far from the required 15 students. So this year the course Ngành Tiếng Việt và Văn Hoá Việt Nam will not start. Maybe after TET 2025?
In January 2025 we indeed got an email, but it was only directed to 5 people. The course will not start in the summer semester, so we will have to wait for the winter semester in September 2025.
July 2025 – Hope from Dr. Tâm
I had already contacted Mrs. Tâm on March 11th, and we had a short phone converstion. She wanted to organize study sessions over zoom, but got no permission from administration.
A renewed conversation on July 7th from Núi Dinh lead to a personal meeting at the Su Pham university on Junly 8th. And this gave me new hope, the requirements by the administration are lowered to just 10 people! I prepared the documents.
After the health check on July 25th I finally submitted all documents on July 30th. With just one day left until the deadline for any application it is frightening to know that we have only 3 applicants so far!
September 2025 – we are at go!
My inquiry on September 3rd lead to the responso to please wait a little longer. So I visited on September 15th, and got a great message: The course will start! At the end of the week, on Friday September 19th, I got an email with the now 4 students that would start this bachelor course in the K51 kohort. It’s the 51st year since the university was founded in 1975. More history would follow in December. But first, the enrollement with 400 other students on September 21st:
Yes, when they talk about foreign students, they do look at me. Even though one other student is present, but since he is from China, he looks to Asian to stick out. The two other students from China and Korea are not yet in Vietnam.
October 2025 – Three more students from Laos and China
My student numbers is 51.01.615.002. The 51 stands for 51st kohort, 01 for regular student (not doctorate or higher), 615 for my course at the foreign languages faculty and I’m the second student. By the end of September we all payed, and I have to spent 2 weeks in Cambodia to get my visa. The application process at the immigration office in Saigon can’t be started unless I’m outside Vietnam, so I drive to Cambodia on October 7th and the application is submitted on October 8th.
On October 16th my invitation letter is finally there! You can get the visa at the embassy in Phnom Penh on this very day, but with some extra fee of 205 USD. If you wait 3 working days (until Monday next week, October 20th) it is only 160 days. And if you can wait 5 working days, it’s only 145 USD. Compared to my expenses in PP it makes sense to wait the extra days until Monday. And I get a lot of stuff done in the coffee shops in this time.
We officially start on October 27th, 5 weeks after the welcome ceremony on September 21st. But I’m in Hanoi for a wedding, and two more students are still in China. So we meet virtually on Google Meet – that does not work in China. We figure out, that Zoom does not work either. But Dr. Tâm is welcoming us all and giving us the important information we need.
Two weeks later, on November 10th, I’m finally in class in person! Time to learn Vietnamese, with 7 weeks delay. To catch up will take some time. But we’re still not complete!
One week later our department postpones the celebration of Teachers day from Thursday, November 20th to Tuesday, November 18th. Now we have at least a group picture of 6 of us in the auditorium with 600 Vietnamese students:
6 students on November 18th in the auditorium
Read more about it at Teacher day in Vietnam. One day later (November 19th) we’re finally complete!
So what is the history of course 615 – Ngành Tiếng Việt và Văn hoá Việt Nam? A conversation with Mrs. Tâm on Friday, December 19th, gives me further insight.
Course 615 in the past
When we open our book 1 and 2, we see that the printing was ordered 1000 copies of book 1 in 2016 (with two different editions in our class) and 500 copies of book 2 in 2015. This is at least the second iteration, only book 4 should still be very old.
In the years prior to Covid-19 many students from Korea attended the university to learn Vietnamese. Their parents worked at companies in Saigon, and large classes of up to 35 students learned more about the Vietnamese language and culture of Vietnam.
Another group signing up for university were students from Afrika. One student was also signing up his sister, father, mother and aunt. For about 1000 USD each got a one year multi entry visa for Vietnam that would otherwise be more expensive or not attainable. But the immigration office had already started to crack down on this practice and required the students to actually show up to class, not just on day one. This “loophole” was already fixed in the 2010s.
But with all the restrictions during the pandemic time the class K45 (2019-2023) had to start studying online in 2020. With the uncertainty K46 was not started in 2020. While the situation was rather safe in Vietnam, international travel would not have foreigners enter the country, and K45 had already returned home.
In early 2021 Saigon was severly affected by the Omicron variant. And while vaccinations were slowly rolling out in summer, the city went into lockdown from June to August 2021. Many were stuck in Phu Quoc, and three months of only virtual activity meant that there was also no K47.
The numbers then never returned to normal. Currently K48 and K49 have only 2 students, so these 4 students learn together now.
Name of the Class
Years of Study
Number of Students
Minimum number of St.
K45
2019-2023
35
K46
2020-2024
–
K47
2021-2025
–
K48
2022-2026
2
?
K49
2023-2027
2
?
K50
2024-2028
0
15
K51
2025-2029
7
10
Yet without students the ministry of education would eventually delete course 615. This assessment is done every 3 years. Two very low student years and one year without students meant to lower the requirement to just 10 students for K51 – and even that could not be met. Well, we are at least 7 students, and for the second semester we might get some exchange students from Taiwan. So far this course is still alive. Let’s see what happens next year. And if we can finish our bachelor.
Our department celebrates teacher day on November 18th, two days earlier. Then almost all students fit into the 600 seat auditorium. We are still not complete, Dinh is still on a business trip in China. But we have fun!
One day later we are finally complete, here with our teacher Cô Chi:
And one more day we write greetings for our teachers in 8 languages on the board – now Phô Mai is missing.
It’s puzzling to realize how much time I spent to get an education. By 2025 I used 12 years of my life to get professional training, in addition to my 10 years of regular school attendance. That’s right, I don’t have a high school diploma (Abitur in Germany). But I taught high school kids and helped them improve their grades.
Kommunikationselektroniker – 3 years
My first professional education is from vocational training at the Deutsche Telekom AG, Niederlassung Potsdam on the Telegrafenberg. It usually requires 3.5 years, but I could shorten it with 4 other students to just 3 years. The official description is Kommunikationseletroniker Fachrichtung Fernmeldetechnik (communication electronics technician, specialized in telecommunication).
Diplom-Physiker – 7.5 years
I started to study physics at the Humboldt Universität zu Berlin in 2000. This is before the bachelor and masters degree were introduced in Europe following the Bologna process. The diploma I received is now considered equal to a masters degree.
The regular study time (Regelstudienzeit) for physiks is 5 years. But I spent 2 semester at the MSU – Moscow State University (МГУ Моско́вский госуда́рственный университе́т и́мени М. В. Ломоно́сова) in Russia. And I invested 1.5 years into the investigation of HgCdTe Narrow-Gap Semiconductors at the HU and BESSY (Elektronenspeicherring-Gesellschaft für Synchrotronstrahlung mbH). The work is reflected in my diploma thesis “Elektronische Eigenschaften von CdxHg1-xTe mit 0.07 < x < 0.4” (here a link to the document on my personal university homepage).
The diploma system does not have a major and minor part. You are only required to study an additional subject for one semester. I chose physical chemistry (Physikalische Chemie) by Prof. Rademann in 2001 with a practice (many experiments and lab reports) over the summer break. This was really fun!
This degree allowed me to teach Math, Physics, Chemistry and Computer Science at public schools in Germany. In 2012 I finally decided to officially become a teacher and get a teaching license.
Oberstufenlehrer für Mathematik und Physik im Niedersächsischen Schuldienst – 1.5 years
Teachers in Germany study for a master of education at universities. But that is only the first step, therefore called Erstes Staatsexamen (first state exam). To qualify as a teacher you also need to pass your Zweites Staatsexamen (second state exam), which usually requires an additional 2 year training period called Referendariat with a teaching obligation of 10 hours per week and lectures at a specialized institute.
I started my ‘Referendariat’ at the Studienseminar Stade in Lower Saxony. To save costs the state had reduced the training time to 1.5 years. While living in Hofkoh, I was travelling to the Studienseminar Lehramt an Gymnasien (45 kilometers), continued to the Gymnasium Warstade in Hemmoor (another 29 kilometers) and after a day of work with frequent visits to my lectures traveled the 56 kilometers back home on most days of the week. It was a stressful time 2012/08 – 2014/01.
Above the start on August 1st, 2012; Mathe Leistungskurs 12 in Hemmoor 2013 and finally the graduation on January 19th, 2014.
In summer 2015 at the Didacta I realized that there are more then 200 International German Schools around the world! It took a while to make up my mind and collect information, but in February 2016 I started applying for several schools around the globe. Here is the list until April 2016:
Taiwan, Taipei
China, Shanghai Pudong
Egypt, Hurghada
India, Mumbai
Vietnam, Saigon or Ho Chi Minh City
Indonesia, Jakarta
Turkey (now Türkiye), Ankara
Russia, Moscow
I added my resume to the database. Offers from Belgium and Mexico reached me by email.
Teaching in the English language – 5 years
My teaching degree brought me to Saigon in Vietnam, but I only taught for 1 year in German. After that I worked 3 years for the American International School Vietnam and 2 years for the Saigon South International School. The topics span a variety of subjects and include the American curriculum, IB Diploma Program and AP Advanced Placement. For the IB and AP I received special training. Here is a list:
IB Physics HL/SL (training in Jakarta)
Chemistry
Integrated Science 9/10 (biology, chemistry and physics)
MYP Design (training in Bangkok)
AP Physics A (training in Sacramento)
High School Math
AP CSP Computer Science Principles (training in Baltimore)
Live Science
Advanced Automation
From a certain perspective I was successful with my teaching. In IB Physics at the AISVN we never had an SL student receive 6 points, and only one time in the past a student had received 6 points on HL higher level. No one ever got 7 points. I wanted to change that.
My first 2-year course started in 2018, and the results of 2020 were remarkable. All 15 students passed, both SL and HL. And some students received 6 and 7 points as their IB score, both HL and SL. Usually the best subject at AISVN is IB Vietnamese Literature with an average slightly above 6 points, and for obvious reasons. But in 2020 the best subject was IB Physics HL with an average of 6.5 IB points! Two students scored 6 points, two students scored 7 points. I am very proud of my students! AISVN was fun, see post on twitter/X:
The work at SSIS was also both challenging and rewarding. In 2022-2023 I supervised 2 ASAs (after school activities): The SSIS Robotics club with VEX V5 and the game developer club Unity Impact. At the end of the year we also absorbed the remaining students of the Girls Code club into our Unity Impact club.
The start for VEX was not easy, since I was completely new to the program. Until the end of 2022 no student could travel, so we could not take the students to the Signature Event in Taipei at the TAS to give them some experience in this competition. But early 2023 we set a new Vietnamese record for 12 attending teams from 5 schools at the Vietnam National Championship 2023 Spin Up.
And for the first time we had a Middle School Team in Vietnam. Now there were 2 spots available to represent Vietnam at the World Championship in Dallas. And I was coaching both winning teams, so I could travel with both teams to the United States:
We had a great time in Dallas. It was a nice experience for the students, they progressed so much in the coming years and returned to Dallas in 2025!
Now it’s time for me to improve my Vietnamese. I have lived in this country for 9 years already!
Ngành Tiếng Việt và Văn hóa Việt Nam – 4 years
I started applying for Ngành Tiếng Việt và Văn hóa Việt Nam (Vietnamese Language and Culture of Vietnam) at the Trường Đại học Sư phạm TP. Hồ Chí Minh (Su Pham university) since May 2024, but the requirements to start this course were not met. The course is intended for 20 students, the university requires at least 15 students to sign up. By October 2024 we were only 7 Students.
In 2025 the requirements were lowered to at least 10 students, but by the end of the signup period in July 2025 we were only 3 students. September 1st we were 4, and Ms. Tân could convince the board of directors to start the course anyway. It worked, we are now Tân Sinh Viên Khóa 51 of 7220101. My student ID is 51.01.615.002. The opening ceremony on September 21st was only attended by 2 of our students, the others were still in Korea and China. In October 2025 we have already 7 students! I went to Cambodia for 2 weeks to get my 1-year visa.
It will take 4 years to receive my bachelor degree (bằng cử nhân). The story continues until 2029. By then I will have spent 26 years as a student, almost 50% of my life!
Preparation while in Cambodia
Since October 2023 I enjoyed studying in the cafe on the ground floor of the RS II Guesthouse, Phnom Penh. It was named Coffee TodaY. But for 2 months it is already a new restaurant.
The new restaurant is not yet on Google. And from outside it is difficult to see that you can enter the second floor and the A/C area. I figured it out on October 17th and spent the next 3 days there almost the whole time by myself. I got things done.
Then I tried to publish this place on Google Maps. Let’s start with the name:
SPECIALITY IN PORK – បាយ សាច់ជ្រូកជាតិ
I have no idea how to enter Cambodian or Khmer characters with my keyboard. This was the first challenge. I took a picture and used internet services.
The Wifi is named BAY SACH JRUK CHEAT while Google translate reads bay sach chrouk cheate for បាយ សាច់ជ្រូកជាតិ. Here is the explanation from ChatGPT:
The Khmer phrase បាយ សាច់ជ្រូកជាតិ (bai sach chruk cheat) can be broken down like this:
បាយ (bai) → rice (usually refers to cooked rice or a meal)
ជាតិ (cheat) → national, local, or domestic (as opposed to imported or foreign)
So, បាយ សាច់ជ្រូកជាតិ means: 👉 Rice with local pork or Rice with domestic pork — essentially, “pork and rice made with local meat.”
It could appear on a menu to emphasize that the pork is from Cambodia rather than imported.
So, that’s ChaptGPT. Now it’s on Google Maps too. This is the place I wrote this post. And analyzed more than 1500 bank transactions from my old German bank account of the last 12 years.
Vornehmlich war es wohl ein Vortrag mit angenehmer Befragung hinterher. In jedem Fall habe ich mein Diplom verteidigt und damit mein Physikstudium erfolgreich abgeschlossen. Der Vortrag findet sich noch immer unter jener Seite:
Mein Mehrfachvisum für Russland gilt noch bis Ende Januar 2008, außerdem ist der Wohnheimplatz so lange gebucht. Also fliege ich noch für eine Woche nach Moskau. Es ist Dienstwoche und ich kann ein paar alte Freunde besuchen. Vor kurzem hat evanzo alle Daten dieses Servers gelöscht, ich hatte noch keine Datensicherung und daher sind diese Einträge im Nachhinein zur Dokumentation erstellt. War sogar im Kino! Der Kurzbericht:
Heute morgen um 2:30 Uhr bin ich endlich mit der Diplomarbeit fertig geworden. Es muss zwar noch zwei mal gedruckt werden, gebunden und abgegeben – aber ich bin geschafft. Wer sie nachlesen möchte und sich schon immer für “elektronische Eigenschaften von CdHgTe” interresiert hat, der kann ja einen Blick ins Internet werfen:
Heute konnte ich eine Art Schlussstrich unter die vergangenen 3 Monate in Moskau ziehen. Vor der Arbeitsgruppe für Tieftemperaturphysik habe ich meine Ergebnisse auf russisch (Определение Электронной Зонной Структуры CdHgTe Методом Угловой Фотоэлектронной Спектроскопии) präsentiert. Das pdf-File des Vortrages findet sich hier. Ich hatte nur 20 Minuten geplant, aber es wurde über eine Stunde.
Für drei Monate geht es wieder nach Moskau. Da kann man in so einem Blog ohne viel html-Kenntnisse und nur mit einem Browser die Heimatwelt über den aktuellen Stand der Dinge informieren. Also starte ich hier damit …
Parallel dazu habe ich auch eine Subdomain mit einem weiteren Bericht erstellt, er findet sich unter russland4.saiht.de
Was ich noch nicht weiss: Die Domain ist bei evanzo gehostet und obwohl jene sich professionell mit Servern auseinandersetzen (und nicht wie ich als Privatperson) so sind doch meine Daten nicht sehr sicher in ihren Händen.
Für drei Monate geht es wieder nach Moskau. Da kann man in so einem Blog ohne viel html-Kenntnisse und nur mit einem Browser die Heimatwelt über den aktuellen Stand der Dinge informieren. Also starte ich hier damit …