| AVS 63rd International Symposium & Exhibition | |
| Thin Film | Monday Sessions |
| Session TF+PS+SE-MoA |
| Session: | Plasma-based Deposition Techniques and Film Characterization |
| Presenter: | Mewlude(Maiwulidan) Imam (Yimamu), Linköping University, Sweden |
| Authors: | M. Imam (Yimamu), Linköping University, Sweden C. Höglund, Linköping University and European Spallation Source ERIC, Sweden R. Hall-Wilton, European Spallation Source ERIC, Sweden J. Jensen, Linköping University, Sweden S. Schmidt, Linköping University and European Spallation Source ERIC, Sweden I.G. Ivanov, Linköping University, Sweden J. Birch, Linköping University, Sweden H. Pedersen, Linköping University, Sweden |
| Correspondent: | Click to Email |
A novel design for neutron detectors based on thin films that are rich in the 10B isotope has been suggested for the European Spallation Source (ESS), in order to overcome the very limited availability of 3He. The detector design uses 10B4C films deposited onto both sides of neutron transparent substrates, e.g., Al blades [1]. The use of aluminum (melting point at 660 °C) limits the deposition temperature for CVD processes and the use of chlorinated precursors due to etching of Al by HCl. Therefore, reactive organoborons are evaluated as precursors for these films using both thermal CVD [2, 3] and plasma CVD.
Plasma CVD of BxC thin films has been studied by introducing the organoborons trimethylboron B(CH3)3 (TMB) or triethylboron B(C2H5)3 (TEB) into a microwave-induced Ar plasma without using any intentional substrate heating. The effect of plasma power, TMB or TEB to Ar ratio and total pressure on the film composition, morphology, density, chemical structure and internal stress were investigated by means of Tof-ERDA, SEM, XRR, XPS and HRXRD, respectively. Tof-ERDA results showed that the highest B/C ratio of 2 was achieved when using TMB at high plasma power. Densification of the films was accompanied by decreasing the total pressure below 0.4 mbar, resulting in a columnar film with densities of 2.16 ± 0.01 g/cm3. The H content in the films was high (15±5 at. %) due to the low substrate temperature (~300 oC). XPS revealed that films deposited using TMB mainly contained B-C bonds and small contribution from C-C/CH bonds, that was evidenced by the observed amorphous carbon phases in the films by Raman spectroscopy. The internal compressive stresses in the films were increased with the Ar gas flow causing film delamination, while a low flow of Ar showed good adhesion and stress level is less than 300 MPa. In addition, the plasma composition studied by optical emission spectroscopy (OES) showed that BH, CH, C2 and H lines were the most intensive lines in the spectrum. Considering the high H content in the films, we propose that BH and CH are the most likely species to contribute to the film formation.
[1] R. Hall-Wilton et al. IEEE NSS/MIC conference record, 2012, 4283
[2] H. Pedersen et al. Chem. Vap. Deposition2012, 18, 221
[3] M. Imam et al. J. Mater. Chem. C2015, 3, 10898