Wolfgang Hillen Summer School 2016

Dr. Nicholas Alt

FAU Erlangen-Nuremberg, Process Machinery and Systems Engineering

Cauerstraße 4
91052 Erlangen
Phone +49 9131 85-29456
Fax +49 9131 85-29449

Dr. Siddha Pimputkar

UC Santa Barbara Materials Department / SSLEEC

Eng II. Bldg. 503 Rm. 1355
Santa Barbara, CA 93106-5050
Phone +1 312 479 4859
Fax +1 805 893 8983

1st Ammonothermal Crystal Growth Summer School:
Optical Active, Nitride-based Semiconductor Materials

July 16-23 2016 – Erlangen, Germany & September 21-26 2016 – Santa Barbara, California, USA

The aim of the summer school is to gain detailed insight into the ammonothermal process by cross-pollinating ideas between two leading universities in the field. Friedrich-Alexander-University (FAU) Erlangen-Nuremberg has established itself to be a leader in characterizing and analyzing the chemistry and properties of the supercritical ammonia fluids, while the University of California, Santa Barbara (UCSB) and start-ups in the area have demonstrated strong knowledge and capability to produce high growth-rate, high quality crystals. Hands-on training provided by students and researchers at both institutions will pass on vital knowledge and the ‘art’ of the science which cannot be communicated through any other means.

For roughly 10 students from Germany and 10 from the USA, the unique opportunity will be provided to learn from leading and honored experts in the field through lectures and by hands-on training in the lab at both locations. The program entails a two-part program, one session in Erlangen, Germany and one in Santa Barbara, California, USA. In Erlangen, the focus will lie on process engineering, while in Santa Barbara, crystal growth will be the focus. To maximize the knowledge transfer, the school will be split into two parts. The theoretical knowledge will be conveyed though symposia with invited speakers (among others, the Gottfried Wilhelm Leibniz Prize winner Prof. Schnick and in addition pending his availability, Nobel Laureate Shuji Nakamura may provide an inspirational talk to the visiting scholars) providing background and applied insight, while the experimental part will allow the students to observe and partake in operating single measurements techniques relevant to the ammonothermal process. The results of the experimental undertakings by each student will be presented at the end of the school to each other.

The expectations of this event are the start of some fruitful scientific cooperation with the goal of finding novel III-nitrides and grow bulk crystals for optical-active and semi-conductor applications.


Final Report (Part 1: July 16th - 23th 2016)

The first session of Wolfgang-Hillen-summer school 2016 was held in Erlangen, at Friedrich-Alexander-University of Erlangen-Nuremburg (FAU) from 16. till 23. of July. Among the participants from the Ludwig-Maximilians-University Munich, the University of Stuttgart, the University of California, Santa Barbara as well as Friedrich-Alexander-University Erlangen-Nuremburg were experts from very different disciplines of ammonothermal growth of single crystals. There were many opportunities offered to get connected and to learn from each other thru the presentations, meetings and mutual work at the lab.

At the beginning of the summer school the participants got to know each other due to a city tour through Erlangen. The ensuing teambuilding event in Franconian Switzerland in a high-ropes yard and the guided tour through the Devil's Cave in Pottenstein deepened the connection between the participants before the work at the lab and the lectures could begin.

The students and PhD candidates were divided into mixed groups for practical lab work. The results of the experiments generated during the week were analyzed and presented to the plenum. The lab practical offered the opportunity to inquire about the work and research results of the group members as well as to conduct critical discussions on working methods. Lecturers delivered by docents from the universities as well as ones by experts in the fields of crystal growth, chemistry and process engineering gave insights into the subject areas and the current state of research. In addition to the lab work and the lectures, an excursion to the company Osram in Regensburg was arranged, in which the industrial production of optically active semiconductors was visited.

The well-made mixture of lectures, lab practical and interdisciplinary exchange has made the summer school a great success for all participants. The knowledge gained and the new contacts with other researchers will positively influence the performance of the individual. The expectations for the second part of the summer school in Santa Barbara in the end of September were accordingly high.

Final Report (Part 2: September 21th - 26th 2016)

On 20. September, delegations of students and PhD candidates from Erlangen, Munich and Stuttgart flew to sunny California in the 90,000-inhabitant city of Santa Barbara. After a brief safety training, the students and PhD candidates were already fully involved in the research work of the Materials Science Department at the University of California, Santa Barbara. A special field of research here is in the growing of bulk GaN. The aim was to set up and evaluate a complete growing experiment over the duration of the summer school. First, the Bavarians were guided through the laboratories and got a detailed insight into the methods and expertise of the Americans. In a first small discussion session, both parties were able to discuss improvements and suggestions for future work. Sealing concepts were explained and new concepts of the measurement technique for the ammonothermal synthesis process which is difficult to access (temperatures up to 600 °C at pressures up to 3000 bar) were discussed.

Afterwards, the participants were allowed to carry out all the steps to a successful growth experiment by themselves. Due to the long duration of a growth experiment, all analysis steps such as XRD, SEM and FTIR were carried out on previously grown crystals. All laboratory experiments were accompanied by a brisk exchange on the advantages and disadvantages of the partly different methods of the participating universities.

During the time the bulk GaN crystal grew, the participants listened to the lectures relevant for the subject, among others Nobel Prize laureate Prof. Dr. Shuji Nakamura on the importance of equipment development. Further lectures focused on crystal growth from solutions, defects in bulk GaN, ammonobasian growth of GaN crystals and optical characterization of GaN crystals.

In addition to mutual dinners, a team event for all participants was organized in order to connect on a personal level. On Sunday we went to a ferry which brought us to the protected nature Chanel Island Santa Cruz. There are only a limited number of tourists per day gaining access to the island. Already on the way dolphins and sea lions were sighted. Sea currents have undermined the cliffs of the island in thousands of years. The highlight of the event was a canoe trip through these caves. Afterwards there was some time for a common hike and exploration of the unique animals of the island.

At a common dinner, all the participants had their farewell celebration. This summer school provided fresh ideas on a professional level and brought all universities closer together. The summer school has already led indirectly to a first scientific exchange project, which hopefully will be followed by others.



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