Substrate Treatment

 

TSST Substrates For the deposition of thin films substrates with well-controlled surfaces are required. The usual mechanical and chemical polishing methods lead to a smooth surface, but cannot control the structure on an atomic level.

Twente Solid State Technology BV offers a special treatment of standard substrates, such as SrTiO3, LaAlO3, or NdGaO3, to control the surface quality of these single crystalline substrates.

Using chemical treatment and subsequent anneal steps, the surface of the substrate recrystallises and steps of exactly one unit cell height result. By using substrates with a low miscut angle, atomically flat terraces with large area can be obtained. These substrates are, among other applications, ideal for fundamental studies of thin film growth.

Twente Solid State Technology performs these treatments on a routine basis in close co-operation with several companies specialised in the production of single crystal substrates. The treated substrates can be obtained via these companies, but Twente Solid State Technology also offers this service for research laboratories that supply their own substrates.

 

Description of the process

The process consists of two parts. First, the substrates are chemically treated, where surface contamination and impurity phases are removed. This process is carried out in a cleanroom environment to guarantee optimal results. The second step involves a heat treatment to allow the surface to recrystallise. The time and temperature of this step can be varied depending on the expected miscut angles. After this procedure a surface where only single unit cell high steps are present, is obtained.

 

Substrate requirements

At present a treatment procedure is available for SrTiO3, LaAlO3, and NdGaO3 substrates. The substrates must have been polished prior to the treatment. Substrates can have maximum dimensions of about 1 inch. Customers are requested to contact us for details.

 

Resulting substrates

TSST SubstrateTreatment-AFMAfter the treatment, the substrates have a well-defined surface structure with unit cell high steps. They show flat terraces with lengths that depend on the miscut angle.

The substrates can be delivered accompanied by an Atomic Force Micrograph (AFM) of their surface structure. When an AFM has been made of the surface, the exact miscut angle can be determined based on this measurement. The miscut angle determined by this method is within 0.01° from the value determined by X-Ray Diffraction.