A Research On Boron Nitride Synthesis For Resistive Random Access Memory

During the last few decades,boron nitride(BN)has gained prodigious eminence because of its exceptional properties and novel crystallographic structure.These nitrides are indispensable to field-effect transistors,electronic devices,gas storage materials,nanowires,magnetic nanoparticles,high heat-resistant semiconductors,ultraviolet light emitters,including other optoelectronic applications,detectors and also in electronic applications.In short,versatile BN appears to be an emerging source of vitality and vivacity in electronic applications.It is challenging to get high quality BN film,since the processes which govern through high temperatures,high pressures and other rigorous conditions.Perceptibly,all approaches of BN synthesis go through high temperature or pressure and it is hard to control the parameters involved.A low temperature growth of BN is still not well researched.In the first section,BN was deposited on p-type Si(111)substrate via RF sputtering at room temperature using a low power of 120 W with ambient flow of Ar and later,electrical properties were inspected.Different samples were obtained using different growth times from 60 mins to 300 mins.RF sputtering is implied due to its high growth rate yields and upscaling potential.The flexibility of choice,large area deposition conformability,maintaining identical elemental compositions during deposition,are some unique features which contemplate sputtering than other deposition techniques.The X-ray diffraction patterns show that there are no BN related peak.The Raman spectroscopy revealed that grown BN had a wavenumber related to h-BN,i.e.,1370 cm-1.These results indicate that our as-grown BN thin films are amorphous.Proceeding further,the insulation property of the films was examined using a metal-insulator-semiconductor(MIS)structure and is confirmed to be similar to h-BN film.The breakdown voltage,dielectric field strength and dielectric constant values of these fabricated MIS structures were far better than earlier reported.The breakdown voltage was as high as 14.96 MV/cm and the minimum dielectric constant of 2.61 were obtained,which shows strong potential application in the integrated field.The proven insulating nature of BN owns a great reputation in revolutionizing the resistive random access memory(RRAM).A bunch of reports has been made on BN based RRAM yet,these type of RRAM fabrication usually lacks in large scale,longer retentions time of RRAM,dearth of high resistance and low resistance states and less durability.In the second part of this research,an insulating sp2-BN thin films have been synthesized on Si via chemical vapor deposition using NH3BH3 as source material.Later,those have been utilized in the fabrication of RRAM devices.Beginning from the Au/sp2-BN/Si RRAM devices,their bipolar resistive switching was studied.Later,their switching mechanism,along with reproducibility,has been checked.The proposed devices were compared with Au/sp2-BN/Cu based RRAMs and device-to-device variability and cycle-to-cycle endurance were not seen prominently.The longer retention time,good resistance states and durability of Au/sp2-BN/Si RRAMs have been verified by conducting various characteristics.The fabricated device showed good uniformity and after 1000 cycles a little decrease in performance was seen,showing good device durability.Testing of devices lead to retention time longer than 1×104 seconds and set voltage between 1.475 V and 2.225 V.The resistive characteristics of the device can be explained by the VCM conduction mechanism induced by B vacancy.In the later part of this dissertation,attention has been paid to grow BN on electro-polished Cu foil.BN nucleation density and location are directly subjective to Cu surface morphology,hence the choice was made.The results showed successful growth of BN on polished Cu foil substrate.This type of foldable substrate can be employed in flexible RRAM fabrication.A polished Cu foil was used and results revealed the successful synthesis of h-BN on it and the synthesized film was transferred to Al2O3 via PMMA method.It was proven to be h-BN.