| Since the environmental pollution is increasingly critical,the monitoring of noxious gas has become the focus of attention,which accelerate the development of gas sensor.Two-dimensional materials?2D?have sparked an upsurge research owing to its excellent electrical,optical and mechanical properties.Arsenic phosphorous?AsP?is a 2D semiconductor with direct band gap and high electron mobility,it has been widely studied in the field of photovoltaic devices and photovoltaic devices.Apart from that,monolayer AsP is of great potential to be utilized in gas sensors,but still lacks research so far.In this study,we systematically investigate the sensing behaviors and mechanism of NO,H2S and CH4molecules absorbed on pristine,electric,Si-and Al-doped AsP sheet in basis of density functional theory.In addition,the current-voltage relations were calculated by using the nonequilibrium Green's function to evaluate the sensing performance.The research results provide a theoretical basis for the design and research of gas sensor based on AsP,which is meaningful for promoting the application of single-layer AsP in the field of gas sensor and other electronic devices.At first,the structural and electrical properties of pristine AsP sheet with and without NO,H2S,and CH4 molecules are studied.The results show that the values of adsorption energy and charge transfer after the gas adsorptions are small,the adsorption distances are large,and the changes of DOS and energy band structure before and after adsorption are not obvious.Furthermore,the PDOS figures show that the hybridizations of the atomic orbitals are slight between the gas molecules and AsP.Therefore,the interactions between pristine AsP and NO,H2S and CH4 molecules are weak,which is not conducive to sensing.In order to prompt the sensing performance of pristine AsP,the electric field is applied on AsP.By applying an electric field in the z direction,the interactions between the E-field-AsP and the NO,H2S and CH4 molecules are enhanced in a certain extent compared with that of pristine AsP,since the adsorption energy and charge transfer are increased.To further improve the sensitivity of AsP,the doping of Si or Al atom is performed on pristine AsP.The results show that the adsorption energy and charge transfer of NO and H2S are significantly increased on Si-or Al-doped AsP,and the DOS also change a lot before and after the adsorptions.In addition,the PDOS have obvious orbital hybridization compare with pristine AsP.However,the adsorption energy and charge transfer of CH4 on doped AsP are still relatively small,the DOS and band structure before and after adsorption are almost the same.Therefore,it is possible to utilize Si-or Al-doped AsP as NO or H2S sensing material.To evaluate whether the doped AsP material is suitable for NO or H2S gas sensor,it is necessary to further explore desorption ability and electrical properties.Therefore,the state of bonds is discussed by analyzing the electronic local function distribution.The results show that there is no chemical bond between Si-doped AsP and H2S molecule,while the chemical bonds are formed in Si-AsP/NO,Al-AsP/NO and Al-AsP/H2S systems.The results above manifest that the interaction between Si doped AsP and H2S gas molecule is a strong physical adsorption.Then,the current-voltage relationship is calculated to analyze the change of conductance before and after adsorption,the results show that the current-voltage curve of Si doped AsP change significantly before and after H2S adsorption,indicating the electrical signal generated by the adsorption of H2S can be effectively detected in practical applications.At the same time,the results of work function show that AsP monolayer has different responses when different small gas molecules absorbed on,indicating its high selectivity.These results show that Si doped AsP is of great potential as H2S gas sensor,which lay a theoretical foundation for the development of the next generation of H2S gas sensor. |
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