Experimental and molecular dynamics studies of an ultra-fast sequential hydrogen plasma process for fabricating phosphorene-based sensors

M Rajabali,M Foroutan,B Zabihi,V Fadaei Naeini,A Boudaghi,H Asgharyan,S Mohajerzadeh

doi:10.1038/s41598-021-95463-z

M Rajabali, M Foroutan + Show 5 more

Open Access

https://doi.org/10.1038/s41598-021-95463-z

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Abstract

Low concentration phosphorene-based sensors have been fabricated using a facile and ultra-fast process which is based on an exfoliation-free sequential hydrogen plasma treatment to convert the amorphous phosphorus thin film into mono- or few-layered phosphorene sheets. These sheets have been realized directly on silicon substrates followed by the fabrication of field-effect transistors showing the low leakage current and reasonable mobility for the nano-sensors. Being capable of covering the whole surface of the silicon substrate, red phosphorus (RP) coated substrate has been employed to achieve large area phosphorene sheets. Unlike the available techniques including mechanical exfoliation, there is no need for any exfoliation and/or transfer step which is significant progress in shortening the device fabrication procedure. These phosphorene sheets have been examined using transmission electron microscopy (TEM), Scanning electron microscopy (SEM), Raman spectroscopy and atomic-force microscopy (AFM). Electrical output in different states of the crystallization as well as its correlation with the test parameters have been also extensively used to examine the evolution of the phosphorene sheets. By utilizing the fabricated devices, the sensitivity of the phosphorene based-field effect transistors to the soluble L-Cysteine in low concentrations has been studied by measuring the FET response to the different concentrations. At a gate voltage of − 2.5 V, the range of 0.07 to 0.60 mg/ml of the L-Cysteine has been distinguishably detected presenting a gate-controlled sensor for a low-concentration solution. A reactive molecular dynamics simulation has been also performed to track the details of this plasma-based crystallization. The obtained results showed that the imparted energy from hydrogen plasma resulted in a phase transition from a system containing red phosphorus atoms to the crystal one. Interestingly and according to the simulation results, there is a directional preference of crystal growth as the crystalline domains are being formed and RP atoms are more likely to re-locate in armchair than in zigzag direction.

Highlights

Low concentration phosphorene-based sensors have been fabricated using a facile and ultra-fast process which is based on an exfoliation-free sequential hydrogen plasma treatment to convert the amorphous phosphorus thin film into mono- or few-layered phosphorene sheets
High pressure and high temperature procedures[13], sonication-based m ethods[14] and even the phase transition using the presence of S nI4/Sn15 are the most common techniques employed to realize few- or monolayers of phosphorene through a complete phase transition from red phosphorus (RP) to black phosphorus (BP)
Considering the extensive studies dedicated to the interaction of small molecules and phosphorene[22], after completing crystallization, a phosphorene-based transistor was fabricated showing a mobility value of 105 cm2/Vs and the Ion/Ioff switching ratio of 102 and eventually, to employ it as a practical device, we investigated its sensitivity to different concentrations of L-Cysteine (L-Cys)

Summary

Experimental section

We need to prepare the suitable substrate to start the crystallization process. To scrutinize the evolution of few-layer phosphorene sheets while changing the test parameters, an intensive electrical characterization has been done on samples in different crystallization status For these measurements, p-type silicon substrates with a resistivity of 1-Ωcm and a thermal oxide as the gate insulator (300 nm) have been used. At this point and in order to involve all three parameters in a gradually increasing manner, the innovative sequential hydrogen plasma was introduced It crystallizes the RP layer with an appropriate treatment but forms thin phosphorene layers with no need to any further exfoliation by employing an intermediate thinning step (S5 and S6). This technique would be a new, ultra-fast and high-yield growth technique especially in electrical and bioelectrical applications including sensing the low concentration of L-Cys solution with no trace of degrading during the measurement

Simulation section

Conclusion

Author contributions