ChemFET sensor: Repercussion of Swift Heavy Ion irradiation on nanorods of nickel- 1 based (NRs-Ni ) Metal-Organic framework

: 12 Repercussion of Swift Heavy Ion (SHI) irradiation on nickel-based nanorods of Metal- 13 Organic Framework (NRs-Ni 3 HHTP 2 -MOF) for enhancement in the properties of ChemFET 14 based gas sensor has been investigated. Nanorods of Ni 3 HHTP 2 -MOF were synthesized by 15 chemical method and exposed to C 12+ ions irradiation with fluence 1x10 11 ion/cm 2 and 1x10 12 16 ion/cm 2 . The structural, spectroscopic morphological and optical characterizations were carried 17 out using x-ray diffraction (XRD), fourier transfer infrared spectroscopy (FTIR), atomic force 18 microscopy (AFM) with scanning electron microscopy (SEM) and UV-visible spectroscopy were 19 studied respectively. Whereas the bandgap was calculated from Tauc's plot. The synthesized 20 nanorods of Ni 3 HHTP 2 MOF were drop-casted on gold coated microelectrodes on silicon/silicon 21 dioxide (Si/SiO 2 ) substrate, where silicon layer serves as a gate and gold microelectrodes on 22 silicon/silicon dioxide (Si/SiO 2 ) substrate as a source and drain. The transmutations in material 23 properties due to SHI irradiations were serviceable for enhancing field-effect transistor (transfer 24 and output) properties. 25


28
In the last few years, the Metal-organic framework (MOF) is one of the focusing materials in 29 the research world due to its tunable properties. MOFs are ultra-high porous, large surface area, 30 highly crystalline, high stability material and importantly it can be tunable by altering central 31 metal or organic ligands [1][2][3]. MOFs are helpful in various applications like gas storage, sensor, 32 chemical separations, biomedical imaging, catalysis and drug delivery as precursors for cooking 33 graphite and metal oxides materials [1,2,4]. 34 The most critical problem in front of modern society is a continuous increment in pollutions 35 in terms of air, water, sound etc [5][6][7]. Among these air pollution absorbed through the respiratory 36 system. Above permissible exposure limit (PEL), hazardous gases responsible for immediately 37 life-threatening [8]. Sulfur dioxide is one of the responsible gases for increasing cardiorespiratory 38 mortality and morbidity in human beings as well as the creation of corrosion in nonliving things 39 [8,9]. Therefore, researchers have been focusing on enhancing sensing properties of detectors 40 for detection various gases including SO2 [10][11][12]. Since last few years, MOF has been one of the 41 mostly explored materials for detection various gases including SO2. M. Tchalala[13] et al. 42 reported fluorinated metal-organic frameworks (MOFs) used for the selective removal and 43 sensing of SO2 analytes. Therefore, screening of new materials and their modification for 44 enhancing sensing properties are continuous process in the research area. 45 Since the last few decenniums, sundry materials have been modified extensively by high 46 energy particles (electron, proton) of heavy ions [14][15][16][17]. The irradiation of energetic ion beams 47 were engenders several types of defects in materials like chain scission, ionization or excitation 48 and ion track formation etc. The SHI irradiation is one of the promising implements for material 49 modifications and workable for enhancing electrical properties [18,19]. Zhang et al.[19] studied 50 the performance of SHI irradiated MoSe2 material. The electrical changes were observed by 51 using TMDC-channel field-effect transistors (FETs). Zeng et al.[20] explored the effects of 52 electrical properties in graphene devices by exposing it to energetic ion beam irradiation where 53 graphene was irradiated by 1.79 GeV Ta ions. It was observed that SHI irradiated graphene at 54 lower fluence exhibited optimized field-effect transistors performance, whereas, at higher 55 fluence, devices were significantly depreciated electrical properties after the irradiation process.

61
Researchers have also explored SHI irradiation on various MOF materials, R. Dutta et al.[26] 62 have reported SHI irradiation on NiBTC MOF using 100 MeV O 7+ , which exhibited 63 enhancement in electrochemical sensing properties. Recently P. Sayyad et al.[27] studied the 64 effect of Au ion with 100MeV at fluence 1 × 10 11 ion/cm 2 and 1 × 10 12 ion/cm 2 irradiation on 65 FeBTC MOF. They observed drastic changes for higher ion fluence rate. Moreover, decrease in 66 crystallite size, increase of energy bandgap, decrease in average surface roughness and new 67 functional group (C-H) was observed after SHI irradiation at a higher fluence 1 × 10 12 ion/cm 2 .

68
Recently, we have explored nickel-based NRs-Ni3HHTP2 MOF for detection sulfur dioxide 69 (SO2) using ChemFET modality [28]. However, to the best of our knowledge the influence SHI 70 irradiation for enhancing properties of materials for ChemFET sensing has not been explored so 71 far. In the present work, SHI irradiation has been explored to enhance the ChemFET sensing 72 properties of NRs-Ni3HHTP2 MOF using C 12+ ion with fluence rate 1x10 11 and 1x10 12 ion/cm 2 73 irradiations. The influence of irradiation on the NRs-Ni3HHTP2 MOF was investigated by using 74 structural analysis, surface morphological, electrical and optical properties.

102
The SHI irradiation was carried out by using material science beamline, 15UD Pelletron 103 tandem accelerators at the Inter-University Accelerator Center, New Delhi, India. The scanning 104 area of ion irradiation was 1 × 1cm 2 of devices riding on a ladder which was placed in the 105 irradiated vacuum chamber under 10 -6 mbar pressure. The targeted material irradiated with C 12+ 106 ion with 50MeV at 1pnA for fluence 1 × 10 11 ion/cm 2 and 1 × 10 12 ion/cm 2 .

107
The value electronic stopping, nuclear stopping and range of ions in NRs-Ni3HHTP2 108 were calculated by using the SRIM simulator program. The calculated values were 1647 eV/ Å, The X-Ray diffraction (XRD) was carried out using Bruker D8 Advance having potential 114 difference 40kV and current 40kA with source CuKα (wavelength 1.5406Å). The FTIR spectrum 115 was recorded using Bruker Alpha ATR. For surface morphology, Scanning Electron Microscopy 116 (SEM) and Atomic Force Microscopy (AFM) were carried out by Tescan MIRA 3 LMH and 117 Park XE-7 instruments respectively and UV-Vis spectroscopy done by using Jasco V-750. FET 118 measurements were carried out using Keithley 4200A semiconductor parameter analyzer (SPA).

119
Sensing measurements were performed using indigenously developed dynamic gas 120 sensing setup which was attached with corrosive and non-corrosive mass flow controllers 121 (MFCs) and data performance was recorded using Keithley 4200A. Tedlar bags were used to get 122 the desired concentration of gas analyte. Ni3HHTP2 is 48%. After C 12+ ion irradiation, 2θ angle peak intensity decreases with increasing 131 fluence rate. The resultant distinct 2θ peaks were observed after irradiation materials at 46 o and 132 48 o . The percentage of crystallinity after C 12+ irradiation for fluence rate 1x10 11 (figure 1-a (red)) 133 and 1x10 12 ion/cm 2 (figure 1-a (blue) was 23% and 20% respectively. This result confirms the 134 crystal structure collapse with increase in amorphous phase after SHI irradiation.

265
It shows good selectivity towards SO2 analytes as shown in figure 5-

Sensing mechanism 280
The sensing mechanism is the key factor to understand the sensing behavior of materials. To understand 281 the sensing mechanism, we have calculated bandgap using Tauc's plot as shown in figure 3-b (1,2 and 3).

282
It shows decrease in banggap after SHI irradiation. After SHI irradiation, defects, free radicals and ions 283 were created on sites of materials. These defects act as an electron trapper with adsorption of the oxygen 284 species from gas analytes. Moreover, these defect were responsible for adsorbing oxygen species and 285 creating oxygen ions thereby preventing electron-hole recombination rate [36]. This was responsible for 286 decreasing drain current after exposing to gas analyte as shown in figure 6. The NRs-Ni3HHTP2 MOFs were successfully synthesized by the chemical method. The SHI 293 irradiation C 12+ with fluence 1x10 11 and 1x10 12 ion/cm 2 have induced changes in structural, 294 spectroscopic, morphological, optical and FET properties of NRs-Ni3HHTP2 MOFs. The NRs-

295
Ni3HHTP2 MOF was amorphized after SHI irradiation which was confirmed by XRD. The XRD 296 pattern exhibits the creation of defects in irradiated materials. The size of NRs-Ni3HHTP2 MOF 297 decreases with decreasing the surface roughness and form a cluster in irradiated materials which 298 was confirmed from surface morphology by SEM and AFM. The decrease in surface roughness 299 was attributed to discontinuous tracks, which lead to amorphization. The drain current of NRs-300 Ni3HHTP2 MOFs based FET was enhanced due to the trapping of free mobile carriers after the 301 SHI irradiations. The SHI induced surface defects in NRs-Ni3HHTP2 MOFs were responsible 302 for enhancing sensing properties. Therefore, it can be concluded that SHI irradiated NRs-303 Ni3HHTP2 MOFs showed improved material properties which were responsible for enhancing 304 sensing properties.