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Nanodevices Design Based On Boron And Phosphorus And Their Electron Transport Properties

Posted on:2022-05-27Degree:DoctorType:Dissertation
Country:ChinaCandidate:X Y DaiFull Text:PDF
GTID:1481306314457724Subject:Materials Processing Engineering
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With the development of electronic products in the light and intelligent direction,the demand for integration and miniaturization of various electronic components is higher and higher.Nanoelectronic devices with excellent optical,electrical,magnetic and mechanical properties become the ideal components to construct functional devices.Low-dimensional carbon nanostructures,such as graphene and carbon nanotubes,have great application prospects in integrated circuits,and become ideal candidates for future computing and processing equipments.However,low-dimensional carbon materials as electronic devices have many disadvantages,for instance,graphene has zero band gap,carbon nanotubes have the chirality-dependent electronic properties,which hinder their practical applications.Boron and phosphorus are the elements adjacent to carbon in the periodic table,their nanomaterials are expected to overcome the shortcomings of carbon nanomaterials and then replace them.It is of great significance for the design and application of future electronic devices.Both theories and experiences have proved that 2D boronphene,phosphorene and ID boron nanotube have potential applications in multi-functional electronic devices.However,due to the limitation of experimental technologies,the relationship between the structure and electron transport properties of these boron/phosphorus-based nanomaterials has not been well understood.In order to reveal the relationship between nanostructures and properties,explore the methods to control the electronic properties,satisfy the needs of multifunctional electronic devices,further theoretical research is urgently needed.Herein,the electronic structures of a series of low-dimensional nanomaterials based on boron and phosphorus were studied by using density functional theory(DFT)based on the first-principles combined with nonequilibrium Green's function(NEGF)methods.And a series of special properties,such as field-effect transistor(FET)characteristic,negative differential resistance(NDR),rectifying characteristic were found.The relationship between atomic structures and electron transport properties was revealed.A variety of methods to control the electron transport properties of nanomaterials were proposed,which provide theoretical guidance for the design of multifunctional electronic devices.The main contents and results of this thesis are as follows:(1)A series of boron-based nanostructures were designed,including B atom concaved boron nanotubes,boron arsenide nanotubes with different cross-section shapes and chirality,and their electron transport properties were studied.It is found that for the armchair ?-boron nanotubes with small diameter,due to the special electron deficiency of B atom(B 2s22p1),the concave deformation design of boron atoms in hexagonal center can compensate for the lack of the electronic defects by delocalization and improve the structural stability of boron nanotubes.In addition,a unique metal-semiconductor transition after B atom concave occured in the armchair?-boron nanotubes.This discovery is expected to make up the shortcoming of CNTs that the electronic properties vary with the chirality,and then achieve the goal of preparing nanotube devices with single electronic properties.The BAs nanotubes with different cross-section shapes(circular,square,elliptical)proposed in this study were theoretically stable and have chirality-independent semiconducting properties,which also overcome the disadvantage of chirality-dependent for carbon nanotubes.The reason is that,regardless of the chirality and cross-section shape,the electrons of the highest occupied valence band(HOVB)orbit are distributed on As atoms,while that of the lowest unoccupied conduction band(LUCB)orbital are located on B atoms.As and B atoms control the transmission peaks below and above the Fermi level respectively,resulting in similar electron transport properties.In addition,the LUCB crosses through the Fermi level after the encapsulation of H2O molecules in the circular BAs nanotubes,which leads to the unique NDR phenomenon and metal-semiconductor transition behavior in the electron transport curve of the device.This novel characteristic proved that the circular BAs nanotube device can be applied in the field of gas sensors.(2)Based on phosphorus,black phosphorus nanotubes doped with C and O atoms as well as the bilayer van der Waals(vdW)heterostructures composed of black phosphorene/blue phosphorene and graphene/silicene/germanene were designed and their electronic properties were calculated.It is found that doping black phosphorus nanotubes with C and O atoms can effectively control the electronic properties of black phosphorus nanotubes,produce different conductive properties and different degrees of NDR characteristics,which has crucial applications in the oscillating circuits.It is also found that the Dirac point of graphene is retained in the bilayer vdW heterojunction constructed by black phosphorene or blue phosphorene with graphene due to the weak hybridization between C and P atoms.However.the strong hybridization between P and Si,Ge atoms leads to the disappearance of Dirac points of silicene and germanene in black phosphorene/silicene(germanene)and blue phosphorene/silicene(germanene)heterojunction,however,small band gaps are generated near the Fermi level.The results showed that bilayer P-based vdW heterojunctions constructed with different 2D materials have different electronic structures,which can meet the requirements of different devices and components.(3)Considering the biocompatibility of black phosphorus,phosphorene nanogap devices combined with neurotransmitters or amino acids were designed to explore the application of phosphorene nanogap devices in biomolecule detection.It is found that a series of different electron transport properties are generated after phosphorene nanogap devices capture biomolecules,which can be used in the biomolecule detection.In particular,acetylcholine(ACh)produced a unique current peak of 600 nA at low voltage(1.1 V),but this signal did not appear in other neurotransmitters,so it can be used to detect the electrical signal of ACh.It has been proved that this unique electrical signal originates from the unique N+(CH3)3-structure in ACh.When ACh is decomposed into choline containing N+(CH3)3-structure,this unique electrical signal still exists,but the peak value of signal current decreases from 600 to 353 nA.Therefore,this unique current signal can not only distinguish ACh from other central neurotransmitters quickly and accurately,but also from other similar substances such as choline.When the N atom of N+(CH3)3-structure is replaced by P atom,the electrical signal appears in the negative bias,but no electrical signal appears in the positive bias.This discovery can provide theoretical guidance for the manufacture of artificial materials with excellent performance.We also found that it is theoretically feasible to distinguish 20 amino acids by identifying the differences of electron transport characteristics(such as the asymmetry of current-voltage curve,current values,etc.)and further apply it into amino acid sequencing of peptides.In addition,different rectifying characteristics have been detected in the series of black phosphorene nanogap biomolecular devices,which make them the candidate materials for biomolecular rectifiers.(4)Combining boron with phosphorus,the boron phosphide nanoribbons passivated by hydrogen or hydroxyl,boron phosphide/boron arsenide nanosheet sandwich heterostructures and boron phosphide/boron arsenide coaxial double-walled nanotubes were designed.The electronic structure of nanomaterials based on boron phosphide with deformation,interlayer micro displacement and nanotube rotation was studied.The results showed that for the zigzag boron phosphide nanoribbons,the hydrogen passivation attracts electrons at HOVB and LUCB to the edge P and B atoms at edges respectively,while the hydroxyl passivation attracts electrons to the O atoms at edges to form ? bond,which makes the hydrogen passivated zigzag BP nanoribbons show direct band gap semiconducting properties,while the hydroxyl passivated zigzag BP nanoribbons show indirect band gap semiconducting properties.Therefore,it is feasible to change the electronic properties of the zigzag boron phosphide nanoribbons by different edge passivation functional groups.In addition,arch,wave and bridge deformations endowed the hydroxy passivated boron phosphide nanoribbons different degrees of NDR characteristics.For the sandwiched boron phosphide/boron arsenide heterostructure,the micro misalignment between layers caused semiconducting-metallic transition,and the inner tube rotation of double-walled nanotube heterostructure can also lead to similar semiconducting-metallic transition.This is because the electron distribution can be rearranged due to the van der Waals force after the interlayer micro misalignment,so that all the nanosheets contribute to the electron transport,leading an extremely high current.In a word,the proposed methods for controlling the electronic structures of nanostructures based on boron/phosphorus can be extended to the electronic structure control of other low-dimensional materials.It provides a theoretical basis for the preparation of functional nano electronic devices and the regulation of their electronic properties.It is of great significance for the preparation and application of low-dimensional materials,the design of multifunctional electronic devices,and the application of low-dimensional materials in integrated circuits.
Keywords/Search Tags:nanoelectronic device, the first-principles, negative differential resistance effect, rectification effect
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