**5. Conclusions**

In summary, we have fabricated highly reproducible high-performance p-channel oxide TFTs on glass substrates using an SnOx channel layer, for which the proper process conditions were selected. The SnO phase was identified and quantified by two independent techniques, XRD and Mossbauer spectroscopy, corroborating the p-type oxide semiconductor behaviour obtained, for films grown at low Opp (around 3%), where the dominant phase is due to α-SnO. The TFTs fabricated show typical saturation mobility of 4.6 cm<sup>2</sup> V−<sup>1</sup> s<sup>−</sup><sup>1</sup> and On-Off ratio > 7 × 104, with threshold voltages of about −10 V, indicating that the devices work in the enhancement mode. This is one of the best stable electrical performances achieved so far for p-type oxide TFTs processed at RT and heat treated at temperatures around 200 ◦C, as the survey conducted concerning the present state of the art in producing p-type TFT based on tin oxide shows (see Tables 1 and 2). This will enable the fabrication of fully transparent CMOS either on rigid or flexible substrates, associated with all the advantages offered by transparent/oxide electronics.

**Author Contributions:** Conceptualization, E.F. and K.J.S.; methodology, R.M.; Structure, morphology, electrical and optical characterization, R.B., P.B.; Mössbauer spectra analysis J.C.W.; validation, E.F., P.B., R.B., K.J.S.; formal analysis, R.B., P.B., L.P.; resources, E.F., R.M.; data curation, P.B., R.B.; writing—original draft preparation, K.J.S.; R.M.; writing—review and editing; overview on the present state of art on p-type TFT SnO based, E.C., R.M.; visualization, E.F., R.M.; supervision, E.F.; project administration, E.F.; funding acquisition, E.F.

**Funding:** This work was partially supported by the European Commission under project INVISIBLE (Advanced Grant from ERC n<sup>º</sup> 228144); BET-EU (H2020-TWINN-2015, GA 692373); TREND (ERC-StG-2016, gran<sup>t</sup> GA 716510); 1D Neon (H2020-NMP-2015-IA, gran<sup>t</sup> 685758-21D). We also acknowledge the FEDER funds through the COMPETE 2020 Program under the project UID/CTM/50025/2013). The authors K. J. Saji thanks Portuguese Ministry of Science and Technology (FCT-MCTES) for offering research grants through the fellowships SFRH/BPD/62942/2009.

**Acknowledgments:** The authors would like to thank Joana Pinto for the support given in measuring the XRD of the films processed as well as the support given by the CENIMAT technical and administrative staff throughout the present study.

**Conflicts of Interest:** The authors declare no conflict of interest.
