Growth And Manipulation Of Four Functional Low Dimensional Structures On Surfaces

The novel physical properties of low-dimensional(LD)structures,including zero-dimensional(0D)quantum dots and single atoms,one-dimensional(1D)nanowires and two-dimensional(2D)thin-film materials,etc.provide a broad research platform for the miniaturization of semiconductor elements and the diversification of high-performance devices.On the one hand,LD structures exhibit rich quantum effects,such as quantum confinement effects,topological states,and strong correlation effects,which will lead to the fabrication of devices with special or excellent functions.On the other hand,the physical properties of LD structures can be effectively improved through growth regulati on,substrate induction or element doping,etc.,and have broad applications in the fields of precision manufacturing,information computing,new energy and biomedicine.Although the relevant research on LD structures has been abundant,there are still many unsolved problems,such as the construction of 0D quantum dots and even single-atom devices at atomic-level precision,the preparation and characterization of nanowires with excellent performance,and the in-situ growth and performance of new 2D materials.LD structures are generally attached to surfaces,and scanning tunneling microscopy(STM)offers unparalleled advantages among all surface in-situ characterization and analysis techniques.Therefore,we combined STM experiments and first-principle calculations to study the growth and manipulation of four LD structures on the surface,and provided corresponding control methods for each of the four systems at different dimensions,realizing partial artificial control,growth and preparation.The main research contents are as follows:Based on STM vertical manipulation and pulse-induced decomposition,the precise implantation of individual phosphorus atoms on the single-crystal silicon surface is realized.Implanting a single phosphorus atom in to silicon is a core step in implementing a solid-state qubit scheme based on a single phosphorus atom.Experiments and theories have proved that the P4 molecule adsorbs on the surface of the silicon with a weak van der Waals force.We have achieved the controllable implantation of single phosphorus atom on the silicon surface by a two-step method using P4 molecules.Step 1: The P4 molecule is "pick-up and "drop-off" at any position on the silicon surface by STM vertical manipulation,achieving atomic-level precise positioning.Step 2: The P4 molecule is decomposed into single phosphorus atom at the target site by STM pulse-induced decomposition for implantation.Compared with the international mainstream Si:P qubit preparation scheme,our method has the characteristics of high implantation accuracy,controllable implantation quantity and strong operability.Based on the decomposition of As4 molecules by gold substrates,a novel 1D arsenic nanochain structure has been fabricated.The armchair arsenic forms a(2×3)supercell structure with the Au(111)surface and remains stable over a wide range of substrate temperature(< 600 K).Theoretical calculations show that the intrinsic 1D arsenic chain has semiconductor properties with a n energy gap of 0.5e V.Comparing the experimental results and theoretical calculations of arsenic grown on other substrates,it is shown that only the Au(111)surface is suitable for the formation of armchair arsenic chains.We have achieved the flip-up of arsenic nanochains on the Au(111)surface through STM tip manipulation,and have proved that arsenic chains can be peeled off from the gold substrate.Compared with the scheme for fabricating 1D arsenic chains in carbon nanotubes,our scheme has the advantages in stable and high-purity arsenic nanochains,simple fabrication and large-scale production.Based on low temperature growth,a high-quality 2D As4 molecular film is fabricated.The tetrahedral-shaped As4 molecules are self-assembled into forming the same ordered structure on the Au(111)and HOPG surfaces in an alternating upright and inverted posture.Experiments and theoretical calculations prove that the interaction between the As4 molecular film and HOPG is significantly weaker than that with the gold substrate.Therefore,the As4 molecular film on the HOPG surface retains more of its intrinsic semiconductor properties.As4 molecular film on the Au(111)surface are two orientations with an angle of 19.1° due to the effects of the Au(111)substrate.By fully understanding the growth mechanism of arsenic on different substrates,the foundation is laid for fabricating high-quality arsenene in the futureBy potassium doping,the electronic structure of the organic picene molecular film is regulated controllably.Picene bulk can be transformed into superconductors by alkali metals doping,but it is controversial whether they are remains superconductivity when this system is reduced to 2D.At first,we have achieved the efficient potassium doping into the picene film on the Au(111)surface by depositing and annealing.With the increase of potassium doping ra tio,several new ordered structures in the Kx Picene films(x = 0 to 4)appear in turn.At the same time,the Fermi level of the potassium-doped picene molecular film gradually moves towards the lowest unoccupied molecular orbital(LUMO)state as the amount of charge transferred from potassium atoms into the picene molecular film increases.Especially,the LUMO state of K3.4Picene is split into two states when is crosses the Fermi energy level,revealing that the system has a strong electron correlation effect,and no superconducting state appears.