Comparison of ECR plasma pretreatment techniques for ZnO atomic layer epitaxy on the sapphire substrate

摘要

ZnO films were grown on sapphire substrates treated with ECR plasma by the atomic layer epitaxy (ALE) technique. ZnO nucleation enhancing effects of oxygen, hydrogen, and argon plasma treatments were compared. The incubation period for ZnO nucleation was measured by using scanning electron microscopy (SEM) and Auger electron emission spectrometric (AES) analysis. The incubation period for ZnO nucleation on the Al_2O_3 substrate not treated with plasma was more than 40 ALE cycles. The incubation period was shortened down to less than 35 cycles by argon or hydrogen ECR plasma pretreatment and to less than 30 cycles by oxygen ECR plasma pretreatment. It was found that a microwave power of 300W and a plasma exposure times of 10 min were appropriate for oxygen ECR plasma treatment of sapphire substrate surfaces to enhance ZnO nucleation. Higher power and longer exposure time would not be effective or would rather aggravate than enhance ZnO nucleation.