A method for charge state regulation based on single molecule debromination defects

Abstract

This invention discloses a method for charge state manipulation based on single-molecule debromination defects. The invention utilizes the localized strong electric field effect generated by an STM tip under low-temperature, ultra-high vacuum conditions. By applying a pulsed voltage with specific parameters, it induces selective debromination reactions in TBTAP single molecules adsorbed on the surface of a metal or superconducting substrate, thereby constructing controllable defect structures at the molecular scale and further enabling the manipulation of the charge response behavior at the defect sites. This overcomes the technical limitations of existing TBTAP molecular assembly systems, which can only achieve unidirectional discharge and cannot obtain resolvable response signals under reverse bias.

Description

Technical Field

[0001] This invention relates to the fields of surface physics, nanoscience and technology and molecular electronics, specifically a method for charge state control based on single-molecule debromination defects. Background Technology

[0002] The manipulation of charge and spin states at the single-molecule scale is a fundamental issue in molecular electronics, quantum information storage, and the construction of nanodevices. The charge state of a single molecule directly determines its intrinsic physicochemical properties, such as molecular energy level structure, electron transport characteristics, redox reactivity, and photoelectromagnetic response. Precisely manipulating the charge state of a single molecule and achieving spatially resolvable control is a key prerequisite for realizing the functional customization of single-molecule devices, precise catalysis of single-molecule reactions, and controllable evolution of quantum states.

[0003] In recent years, TBTAP-like organic radical molecules have been used to construct self-assembled systems on superconducting metal surfaces, exhibiting stable alternating charge distribution structures. In this system, charged anionic radicals... These molecules, arranged in a periodic alternation in space with neutral molecules, can exhibit localized discharge behavior under STM positive bias, displaying typical discharge ring characteristics in the dI / dV space mapping. However, in existing... In the system, due to the limitations of the intrinsic electronic structure of the molecules and the Coulomb interaction in the superlattice, neutral molecules have difficulty regaining electrons and forming a stable charged state response under negative bias conditions.

[0004] Scanning tunneling microscopy (STM), with its atomic-level spatial resolution and tunable electron injection capabilities, has become an important experimental platform for studying single-molecule charge state transitions, the Kondo effect, and Yu-Shiba-Rusinov (YSR) states. However, STM tips can induce structural modification reactions in molecules through localized high electric fields or high-energy electron injection, such as halogen desorption and bond breaking, thereby achieving single-molecule-scale structural transformations. Existing STM-induced debromination methods are mainly used to disrupt existing magnetic states or alter local electronic structures, but have not yet been used to construct functional defect sites capable of activating novel charge-responsive channels.

[0005] Therefore, how to achieve the "transformation of the response capability from the discharge state to the charge state" in a single-molecule system through in-situ controllable defect engineering remains a key unsolved problem in this field. Summary of the Invention

[0006] The purpose of this invention is to provide a method for charge state manipulation based on single-molecule debromination defects. Using the localized strong electric field effect generated by an STM tip under low-temperature, ultra-high vacuum conditions, a pulsed voltage with specific parameters is applied to selectively induce a debromination reaction in 4,5,9,10-tetrabromo-1,3,6,8-tetraazapyrene (TBTAP) single molecules adsorbed on the surface of a metal or superconducting substrate. This allows for the construction of controllable defect structures at the molecular scale and further enables the manipulation of the charge response behavior at the defect sites. This achieves spatially resolvable control of the charge state response in a single-molecule system, providing a new pathway for molecular-scale information storage and reconfigurable molecular systems. It also overcomes the technical limitations of existing TBTAP molecular assembly systems, which can only achieve unidirectional discharge and cannot obtain resolvable response signals under reverse bias.

[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution: A method for charge state modulation based on single-molecule debromination defects, comprising the following steps: In an ultra-high vacuum environment, after cleaning the superconducting metal substrate, TBTAP molecules are deposited onto the superconducting metal substrate by thermal sublimation to form a TBTAP self-assembled molecular layer. A pulsed voltage was applied to the target molecule in the self-assembled TBTAP molecular layer by the tip of a scanning tunneling microscope to induce the target molecule to debrominate and form structural defect points. A reverse negative bias voltage is applied to the structural defect sites formed by the debromination of the target molecule to excite the charging ring and achieve the unlocking of the charging state; Within the same self-assembled molecular network, the state selection and reading of undebrominated molecules and structural defect sites are achieved by utilizing bias polarity, thus realizing spatial separation of charge and discharge behavior.

[0008] According to the above technical solution, the background pressure of the ultra-high vacuum environment is ≤1×10-10mbar.

[0009] According to the above technical solution, the TBTAP molecules undergo thermal sublimation at a temperature of 150℃~200℃ and are deposited on the superconducting metal substrate at a temperature maintained at 100K~250K to form a TBTAP self-assembled molecular layer. Subsequently, the TBTAP self-assembled molecular layer is cooled to a low temperature of 1.0K~4.8K for subsequent scanning tunneling microscopy observation and control.

[0010] According to the above technical solution, the TBTAP self-assembled molecular layer includes rows of charged anion radical molecules and rows of neutral molecules arranged alternately along a preset lattice direction.

[0011] According to the above technical solution, the tip of the scanning tunneling microscope is positioned above the target molecule of the charged anionic free radical molecule row of the TBTAP self-assembled molecular layer. After setting the initial tunneling current and bias voltage in constant current mode, the feedback loop of the STM is turned off, the tip is suspended above the target molecule, and a high voltage pulse with a voltage amplitude of 1.5V to 3.0V and a pulse width of 10ms to 200ms is applied to induce the carbon-bromine bond to break in the target molecule, removing at least one bromine atom and forming a structural point defect in situ, so that the target molecule changes from anionic state. An irreversible chemical structural transformation occurs, forming a neutral state TBTAP0.

[0012] According to the above technical solution, the initial tunneling current is set to 10pA to 1nA and the initial tunneling bias voltage is set to 10mV to 500mV in constant current mode.

[0013] According to the above technical solution, a reverse negative voltage with an amplitude range of -0.4V to -1.5V is applied to the defect site formed by debromination of the target molecule to excite the defect site to generate the conductivity valley feature in the differential conductivity spectrum and the concentric high conductivity charging ring feature in the spatial differential conductivity map, thereby realizing the activation of the charge response channel of the defect site under negative bias voltage.

[0014] According to the above technical solution, the diameter of the charging ring is controlled by adjusting the amplitude of the reverse negative bias voltage; the position and depth of the threshold voltage of the conductivity valley are controlled by adjusting the distance between the STM tip and the sample surface. When adjusting the distance between the tip and the sample surface, for every 10pm~50pm decrease, the absolute value of the threshold voltage of the conductivity valley decreases, and the depth of the conductivity valley increases.

[0015] According to the above technical solution, the specific steps to achieve spatial separation of charging and discharging behaviors within the same self-assembled molecular network include: When a positive read bias is applied, the undebrominated charged anion radical molecules respond to the discharge characteristics and generate a discharge ring, while the debrominated charged anion radical molecules form defect points without response. When a negative read bias is applied, charged anion radical molecules debrominate to form defect points in response to the charging characteristics, generating a charging ring, while unbrominated charged anion radical molecules do not respond.

[0016] Multiple structural point defects are manufactured at predetermined points on the surface of the molecular island according to a preset pattern, forming a regularly arranged defect array, thereby realizing the spatial programmable distribution of charged anion molecules and debromination defect molecules in the molecular lattice.

[0017] According to the above technical solution, the positive read bias voltage is 0.5V to 1.5V, and the negative read bias voltage is -0.4V to -1.5V.

[0018] Compared with existing technologies, the beneficial effects achieved by this invention are as follows: This invention, through debromination defect engineering, enables the TBTAP / Pb(111) system to obtain stable defect charge response signals (charging ring and dip) under negative bias, achieving bidirectional control of positive bias discharge and negative bias defect response, overcoming the technical limitation of existing systems that can only discharge in one direction. Simultaneously, by utilizing the response difference between debromination defect sites and the intact lattice, spatial separation of charging and discharging phenomena at the nanoscale is achieved, supporting high-density arrayed information writing and providing a technical foundation for the construction of programmable molecular spin arrays. Furthermore, the charging ring size and conductivity valley threshold are monotonically adjustable with tip height and bias voltage, resulting in a wide operating window and high repeatability. Attached Figure Description

[0019] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings: Figure 1 This is a flowchart of a method for controlling the charge state based on single-molecule debromination defects; Figure 2 This is a diagram of the rectangular lattice structure of the TBTAP self-assembled molecular layers; Figure 3 This is a measurement of the differential conductivity spectrum of the TBTAP self-assembled molecular layer; Figure 4 This is an STM image of the morphology before debromination; Figure 5 This is an STM image of the debromination process; Figure 6 This is a comparison of dI / dV spectra before and after debromination; Figure 7 This is an STM morphology image of the defect sites after debromination; Figure 8 It is a negative bias dI / dV spectrum of multiple different debromination defect sites; Figure 9 This is the dI / dV mapping diagram at Vs=-1V; Figure 10 This is a comparison of the dI / dV spectra of defective sites and undebrominated sites; Figure 11 The undebrominated sites show a discharge peak characteristic at approximately 1V; Figure 12 This is a diagram showing the transformation of the charging ring under different bias voltages. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] This embodiment provides a method for charge state manipulation based on single-molecule debromination defects, such as... Figure 1 As shown, the specific steps include: Step 1: Provide a superconducting substrate and a TBTAP self-assembled molecular layer; Under ultra-high vacuum conditions (pressure ≤ 1 × 10⁻¹⁰ mbar), the superconducting metal substrate was cleaned, and 4,5,9,10-tetrabromo-1,3,6,8-tetraazapyrene (TBTAP) molecules were thermally sublimated and deposited on the Pb(111) substrate at a temperature of 150 °C to 200 °C. Subsequently, the TBTAP self-assembled molecular layer was cooled to a low temperature of 4.8 K for subsequent scanning tunneling microscopy observation and control.

[0022] TBTAP molecules spontaneously assemble to form a dense rectangular lattice structure, such as... Figure 2 As shown in Figure a, where, as Figure 2 In the diagram, 'a' represents the STM topography (Vs=0.8V), and the dashed lines represent the neutral molecule row 'n' and the charged molecule row 'c', respectively.

[0023] This lattice contains alternating rows of n neutral molecules and c rows of c charged anion molecules, i.e. ,like Figure 2 As shown in b. Figure 2 In the diagram, 'c' represents the dI / dV mapping under positive bias (Vs=0.8V), showing that the discharge ring only appears in the charged molecule row c.

[0024] Its charge-carrying property was verified by differential conductance (dI / dV) spectral measurement under positive bias (Vs=0.8V), such as... Figure 3 As shown, a pair of symmetrical Yu-Shiba-Rusinov (YSR) state resonance peaks were detected within the superconducting band gap at the c-row molecule (located in...). (The location) proves that the molecule has a magnetic ground state with spin 1 / 2.

[0025] Step 2: Apply pulsed voltage using the STM tip to induce debromination of the target molecule and form defects; Position the target using an STM tip (superconducting Pb tip). Molecules (target) Molecules in Figure 4(As shown by the green dot in section a). With the feedback loop closed, the needle tip is suspended over the target molecule, and a voltage pulse with specific parameters is applied. Figure 4 In the diagram, b represents the dI / dV mapping under positive bias, and the area circled in red dashed circle is the discharge ring.

[0026] In this embodiment, the pulse voltage amplitude is 1.5V~3.0V, and the pulse width is 10ms~200ms. After the pulse is applied, the target molecule undergoes a debromination reaction, removing bromine atoms and forming point defects, such as... Figure 5 As shown in Figure a, Figure 5 The red dot in the middle (a) marks the defect site. After debromination, the STM morphology of this site changes significantly, while the surrounding molecular lattice remains intact. This method allows for the on-demand fabrication of multiple defects on the surface of molecular islands, forming a regularly arranged defect array, such as... Figure 5 As shown in b, Figure 5 In the diagram, b represents the dI / dV mapping under positive bias. The red dashed circle indicates the original position, showing that there is no discharge ring at the defect site.

[0027] Step 3: Apply a reverse negative bias voltage to the defect site to excite the charging ring and activate the charge response of the defect site; After debromination, the molecule irreversibly transforms from an anionic state to a neutral state. .

[0028] First, verify the debromination effect: such as Figure 6 As shown, after debromination (red line), the original... YSR resonance peak of molecules The complete disappearance of the defect proves that the molecular spin state has been eliminated and the state has become neutral. Simultaneously, under positive bias, the discharge ring no longer appears at this defect site.

[0029] Then, charged-state excitation is performed: a reverse negative bias is applied to the neutral defect site. For example... Figure 7 As shown, the STM morphology (Vs=0.5V) of the debromination defect sites undergoes significant changes. The inset in the upper right corner (Vs=-0.54V) reveals distinct concentric ring-shaped high-conductivity features around the defect sites, i.e., "charging rings." This indicates that the debromination defect sites unlock the ability to acquire electrons from the substrate.

[0030] Meanwhile, dI / dV spectral measurements revealed that each debromination defect site exhibited a distinct conductivity trough (dip), while surrounding undebromination sites showed conductivity peaks, such as... Figure 8 As shown, this demonstrates that the phenomenon of unlocking negative bias charging capability due to debromination defects has high universality and repeatability.

[0031] Furthermore, for individual defect sites, such as Figure 9As shown, as the STM tip approaches the sample surface (from 0 pm to -87 pm), the absolute value of the threshold voltage of the dip decreases and the depth of the dip increases, proving that the intensity of the defect response signal can be precisely and quantitatively controlled by the tip height.

[0032] Step 4: Spatial separation of charging and discharging behavior is achieved through bias polarity selection; First, the electronic state difference between defect sites and undebrominated sites was verified through dI / dV spectroscopic characterization: such as Figure 10 As shown in the comparison between (a) and (b), the undebrominated sites retain the YSR peak and show no negative bias charging response; while the YSR peak disappears at the debrominated defect sites, and a conductivity valley (dip) appears under negative bias. Figure 11 As shown, the undebrominated sites exhibit a discharge peak at a positive bias voltage of approximately 1V.

[0033] Furthermore, spatially selective readout is performed within the same self-assembled molecular network: when a forward readout bias (Vs = 1.0V~1.2V) is applied, undebrominated... In the dI / dV space mapping, the molecule exhibits a discharge loop, while neutral defect sites show no response; when a negative read bias is applied (Vs = -0.6V or -1V), the neutral defect sites exhibit a charging loop in the dI / dV space mapping, while undebrominated molecules show no response. For example... Figure 12 As shown, as the absolute value of the negative bias voltage increases from 0.6V to 1V, the diameter of the charging ring increases accordingly, verifying the quantitative control of the bias voltage amplitude on the size of the charging ring.

[0034] By using the pulse voltage induction method in step 2, multiple defects are manufactured at fixed points on the surface of the molecular island according to a preset pattern. Charging rings can stably appear at all defect sites, thereby realizing the construction of a programmable molecular charge state array and completing the spatial separation of the coexistence and charging / discharging behavior of charged anion molecules and debromination defect molecules in the molecular lattice.

[0035] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0036] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for charge state manipulation based on single-molecule debromination defects, characterized in that, The steps include: In an ultra-high vacuum environment, after cleaning the superconducting metal substrate, TBTAP molecules are thermally sublimated at a temperature of 150℃~200℃ and deposited on the superconducting metal substrate at a temperature maintained at 100K~250K to form a TBTAP self-assembled molecular layer. Subsequently, the TBTAP self-assembled molecular layer is cooled to a low temperature of 1.0K~4.8K for subsequent scanning tunneling microscopy observation and control; wherein, the background pressure of the ultra-high vacuum environment is ≤1×10-10 mbar. Using a scanning tunneling microscope (STM) tip, a pulsed voltage is applied to a target molecule in a TBTAP self-assembled molecular layer containing charged anion radical molecules to induce debromination and the formation of structural defect points. Specifically, the STM tip is positioned above the target molecule in the TBTAP self-assembled molecular layer containing charged anion radical molecules. After setting the initial tunneling current and bias voltage in constant current mode, the STM feedback loop is turned off, the tip is suspended above the target molecule, and a high-voltage pulse with a voltage amplitude of 1.5V to 3.0V and a pulse width of 10ms to 200ms is applied to induce the carbon-bromine bond to break in the target molecule, forming structural point defects in situ. A reverse negative bias voltage is applied to the structural defect sites formed by the debromination of the target molecule to excite the charging ring and achieve the unlocking of the charging state; Within the same self-assembled molecular network, the state selection and reading of undebrominated molecules and structural defect sites are achieved by utilizing bias polarity, thus realizing spatial separation of charge and discharge behavior.

2. The method for charge state control based on single-molecule debromination defects according to claim 1, characterized in that, The TBTAP self-assembled molecular layer comprises rows of charged anionic radical molecules and rows of neutral molecules arranged alternately along a preset lattice direction.

3. The method for charge state control based on single-molecule debromination defects according to claim 1, characterized in that, In the constant current mode, the initial tunneling current is set to 10pA to 1nA, and the initial tunneling bias voltage is set to 10mV to 500mV.

4. The method for charge state control based on single-molecule debromination defects according to claim 1, characterized in that: A reverse negative voltage with an amplitude range of -0.4V to -1.5V is applied to the debromination defect site of the target molecule to excite the defect site to generate a conductivity valley in the differential conductivity spectrum and a concentric high conductivity charging ring in the spatial differential conductivity map.

5. The method for charge state control based on single-molecule debromination defects according to claim 4, characterized in that, The diameter of the charging ring is controlled by adjusting the amplitude of the reverse negative bias voltage; the relative distance between the STM tip and the sample surface where the structural defect site is located is adjusted to control the threshold voltage position and depth of the conductivity valley.

6. The method for charge state manipulation based on single-molecule debromination defects according to claim 1, characterized in that, The specific steps for achieving spatial separation of charge and discharge behaviors within the same self-assembled molecular network include: When a positive read bias is applied, the undebrominated charged anion radical molecules respond to the discharge characteristics and generate a discharge ring, while the debrominated charged anion radical molecules form defect points without response. When a negative read bias is applied, charged anion radical molecules debrominate to form defect points in response to the charging characteristics, generating a charging ring, while unbrominated charged anion radical molecules do not respond.

7. The method for charge state manipulation based on single-molecule debromination defects according to claim 6, characterized in that, The positive read bias voltage is 0.5V to 1.5V, and the negative read bias voltage is -0.4V to -1.5V.

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