The seminar at Técnico featured Spanish expert José Luis Plaza Canga-Argüelles and addressed advances in the production of CdZnTe crystals for medical, aerospace, and nuclear safety applications.
The C²TN – Centro de Ciências e Tecnologias Nucleares – Academy welcomed Professor José Luis Plaza Canga-Argüelles, associate professor in the Materials Science Department, as well as director of the prestigious Crystal Growth Laboratory of Universidad Autónoma de Madrid, Spain, which has been in operation since the 1960s, to the Campus Tecnológico e Nuclear of the Instituto Superior Técnico. His visit included a seminar on the topic ‘Crystal Growth at the Crystal Growth Lab in Madrid: Progress in CdZnTe and CdZnSeTe VGF-Grown Crystals for X and Gamma-Ray Detector Applications’, focusing on advances in crystal growth applicable to radiation detection.
During the seminar, the Spanish researcher presented the latest developments in the production of CdZnTe (cadmium zinc telluride) semiconductor crystals and the quaternary compound CdZnSeTe (cadmium zinc telluride-selenide), using the VGF (Vertical Gradient Freeze) technique, which has high potential for use in X-ray and gamma radiation detectors. The main objective? ‘To manufacture a radiation detectors with crystals grown in our laboratory, carrying out all the intermediate stages in collaboration with other Spanish institutions,’ explained José Luis Plaza.
The seminar also covered various techniques and equipment for crystal growth — such as the Czochralski, Bridgman, Travelling Heater Method (THM) and VGF methods — currently used in the development of other strategic materials, including LiNbO₃ (lithium niobate), GaSb (gallium antimonide), CdTe (cadmium telluride), ZnWO₄ (zinc tungstate) or Si (silicon).
Professor José Luis Plaza explained, in an accessible way, the importance of his work, emphasising that ‘it is essential to growth CdZnTe crystals with high crystalline quality and homogeneous composition’, given that such improvements have a direct impact on radiation detection capabilities, ‘with applications in areas such as nuclear medicine, geology, aerospace research, and devices for detecting X-rays and γ rays’, he added.
With regard to the main challenges addressed, the need to obtain materials with high resistivity and uniform composition was highlighted. The addition of selenium (Se) and the adoption of the most appropriate growth methodology — such as the VGF technique, which has no moving parts and has been developed in his laboratory for over a decade — were identified as promising strategies.
The practical relevance of these crystals is particularly evident in the fields of medical imaging and security. ‘These advances contribute to the development of the next generation of detection systems, such as gamma cameras and positron emission tomography (PET)’, the researcher pointed out.
Regarding other materials under study, José Luis Plaza referred to LiNbO₃ as ‘the “silicon” of photonics,’ essential for devices such as solid-state lasers and non-linear optical systems. GaSb, on the other hand, is considered a key material in the manufacture of semiconductor lasers and thermophotovoltaic cells.
The visit to Lisbon was also an opportunity to strengthen the ties of collaboration between the Universidad Autónoma de Madrid and the C²TN of the Instituto Superior Técnico. ‘The measurements taken in the frame of ‘EURO-LABS’ project are fundamental to our work on radiation detectors, and we anticipate future collaborations’, assured José Luis Plaza.
When asked about the future of research in this area, the professor emphasised the importance of “continuing with analyses and measurements similar to those carried out during this visit to C²TN, in order to improve the properties of the materials and enable the production of next-generation medical detectors”.
In summary, the researcher praised the structure and organisation of the C²TN Academy, stating that seminars of this nature are essential for keeping society informed about advances in scientific fields that have a direct impact on health, safety and quality of life. “Research into radiation detectors has very significant implications for society, from medical diagnosis to international arms control. Staying informed about these advances is essential,” concluded José Luis Plaza.