Yoshimatsu Laboratory
High-temperature substrate heating using extremely focused semiconductor laser light
This PLD chamber controls the growth temperature by heating the backside of the substrate using a semiconductor laser. This allows thin film growth in high-temperature environments that are imaccessible with lamp heating (Tsub ≤ 850ºC). In a PLD chamber with a semiconductor laser heating mechanism, the upper limit for substrate temperature is 1000ºC, and the search for optimal synthesis conditions is also limited to temperatures below 1000ºC. However, this equipment uses extremely focused laser light and a custom-made sample holder for 5mm square substrates, enabling thin film synthesis with stable temperature control up to 1300ºC. By adopting this mechanism, we were the first in the world to successfully synthesize single-crystal thin films of metastable titanium oxide λ-phase Ti3O5 (Cryst. Growth Des. (2022)), and have clarified its structure and electronic phase transition (Phys. Rev. Mater (2024)).
(Left) Relationship between semiconductor laser current and substrate temperature. A significant difference in temperature rise can be seen between normal and focus heating methods, with focus heating reaching 1300ºC at an output of ~25 A. The inset photo shows a substrate heated to 1300ºC as viewed through the viewport.
(Right) Comparison of normal and focus heating methods, along with a photo of the sample holder used.
Homemade Load Lock chamber
A vertical load lock (left) is formed using an AVC hollow Z-stage and two ICF T-tubes, and the sample bank (right) is homemade. Targets and samples can be transferred between the PLD and load lock chambers by moving the bank up and down and the transfer rod left and right. By reducing the volume of the load lock chamber, a vacuum level (~10-7 Torr range) is achieved that allows sample transfer to the PLD chamber in less than 30 minutes, enabling high-throughput experiments.
