Abstract: A nanoscale circuit has an optical antenna receiving the radiation from a mode-locked laser and it responds by transmitting selected microwave or terahertz frequencies with a separate orthogonal antenna. Only MIM diodes, low-pass filters, and a load resistor are used to generate, separate, and transmit at the harmonics of the laser pulse-repetition rate.

Abstract: In order to meet the needs of, in particular, the semi-conductor industry as it requires finer lithography nodes, a method of feedback control for scanning probe microscopy generates a microwave frequency comb of harmonics in a tunneling junction (10) between a probe tip electrode (80) and sample electrode (20) by irradiating the junction with mode-locked pulses of electromagnetic radiation from a laser (90). Utilizing power measurements within one or more harmonics within the microwave frequency comb, the tip-sample distance in the tunneling junction may be regulated by a feedback control (40) utilizing an extremum-seeking algorithm for maximum efficiency and avoid tip crash when used with resistive samples. Ideally, no externally provided DC bias is required to use the method. Utilization of this method contributes to true sub-nanometer resolution of images of carrier distribution in resistive samples such as semi-conductors.

Abstract: In order to meet the needs of the semi-conductor industry as it requires finer lithography nodes, a method of feedback control for scanning probe microscopy generates a microwave frequency comb of harmonics in a tunneling junction by irradiating the junction with mode-locked pulses of electromagnetic radiation. Utilizing power measurements within one or more harmonics, the tip-sample distance in the tunneling junction may be regulated for maximum efficiency and avoid tip crash when used with resistive samples. Optionally, no DC bias is required to use the method. Utilization of this method contributes to true sub-nanometer resolution of images of carrier distribution in resistive samples such as semi-conductors.

Abstract: The superimposition of a periodic potential wave to the tip movement control or the bias supply of an STM, in which a microwave frequency comb is generated in its tunneling junction, may be used to reduce or eliminate artifacts or other noise generated from outside the tunneling junction.

Abstract: In order to meet the needs of the semi-conductor industry as it requires finer lithography nodes, a method of feedback control for scanning probe microscopy generates a microwave frequency comb of harmonics in a tunneling junction by irradiating the junction with mode-locked pulses of electromagnetic radiation. Utilizing power measurements within one or more harmonics, the tip-sample distance in the tunneling junction may be regulated for maximum efficiency and avoid tip crash when used with resistive samples. Optionally, no DC bias is required to use the method. Utilization of this method contributes to true sub-nanometer resolution of images of carrier distribution in resistive samples such as semi-conductors.

Abstract: The superimposition of a periodic potential wave to the tip movement control or the bias supply of an STM, in which a microwave frequency comb is generated in its tunneling junction, may be used to reduce or eliminate artifacts or other noise generated from outside the tunneling junction.

Abstract: A mode-locked laser injects pulses of minority carriers into a semiconductor sample. A microwave frequency comb is then generated by the currents formed in the movement of majority carriers native to the semiconductor and the injected minority carriers. These carriers move to cause dielectric relaxation in the sample, which can be used to determine carrier density within the sample. Measurements require close proximity of transmitter and receiver contacts with the sample and may profile a semi-conductor with a resolution of approximately 0.2 nm.

Abstract: Numerous carrier profiling techniques may be combined for simultaneous operation of those techniques on a single material sample. A single apparatus utilizing a Field-Programmable Gate Array (“FPGA”) may be utilized to simultaneously operate those techniques. Various hardware components necessary for the given techniques may be operationally connected to the FPGA while simulations may be performed and stored with the apparatus for real-time analysis of results.

Abstract: A semiconductor carrier profiling method utilizes a scanning tunneling microscope and shielded probe with an attached spectrum analyzer to measure power loss of a microwave frequency comb generated in a tunneling junction. From this power loss and by utilizing an equivalent circuit or other model, spreading resistance may be determined and carrier density from the spreading resistance. The methodology is non-destructive of the sample and allows scanning across the surface of the sample. By not being destructive, additional analysis methods, like deconvolution, are available for use.

Abstract: A control methodology for scanning tunneling microscopy is disclosed. Instead of utilizing Integral-based control systems, the methodology utilizes a dual-control algorithm to direct relative advancement of a STM tip towards a sample. A piezo actuator and stepper motor advances an STM tip towards a sample at a given distance until measuring a current greater than or equal to a desired setpoint current. Readings of the contemporaneous step are analyzed to direct the system to change continue or change direction and also determine the size of each step. In simulations where Proportion and/or Integral control methodology was added to the algorithm the stability of the feedback control is decreased. The present methodology accounts for temperature variances in the environment and also appears to clean and protect the tip electrode, prolonging its useful life.

Abstract: A semiconductor carrier profiling method utilizes a scanning tunneling microscope and shielded probe with an attached spectrum analyzer to measure power loss of a microwave frequency comb generated in a tunneling junction. From this power loss and by utilizing an equivalent circuit or other model, spreading resistance may be determined and carrier density from the spreading resistance. The methodology is non-destructive of the sample and allows scanning across the surface of the sample. By not being destructive, additional analysis methods, like deconvolution, are available for use.

Abstract: A mode-locked laser injects pulses of minority carriers into a semiconductor sample. A microwave frequency comb is then generated by the currents formed in the movement of majority carriers native to the semiconductor and the injected minority carriers. These carriers move to cause dielectric relaxation in the sample, which can be used to determine carrier density within the sample. Measurements require close proximity of transmitter and receiver contacts with the sample and may profile a semi-conductor with a resolution of approximately 0.2 nm.

Abstract: A control methodology for scanning tunneling microscopy is disclosed. Instead of utilizing Integral-based control systems, the methodology utilizes a dual-control algorithm to direct relative advancement of a STM tip towards a sample. A piezo actuator and stepper motor advances an STM tip towards a sample at a given distance until measuring a current greater than or equal to a desired setpoint current. Readings of the contemporaneous step are analyzed to direct the system to change continue or change direction and also determine the size of each step. In simulations where Proportion and/or Integral control methodology was added to the algorithm the stability of the feedback control is decreased. The present methodology accounts for temperature variances in the environment and also appears to clean and protect the tip electrode, prolonging its useful life.

Abstract: A microwave frequency comb (MFC) is produced when a mode-locked ultrafast laser is focused on the tunneling junction of a scanning tunneling microscope (STM). The MFC consists of hundreds of measureable harmonics at integer multiples of the pulse repetition frequency of the laser, which are superimposed on the DC tunneling current. In Scanning Frequency Comb Microscopy (SFCM) the tip and/or sample electrode of the STM is moved vertically and laterally so that the power in the MFC may be measured at one or more locations on the surface of the sample and, from the power, carrier density, and other characteristics, of the sample may be calculated. SFCM is non-destructive of the sample. While many systems are possible to practice SFCM, a preferred apparatus is disclosed.

Abstract: A microwave frequency comb (MFC) is produced when a mode-locked ultrafast laser is focused on the tunneling junction of a scanning tunneling microscope (STM). The MFC consists of hundreds of measureable harmonics at integer multiples of the pulse repetition frequency of the laser, which are superimposed on the DC tunneling current. In Scanning Frequency Comb Microscopy (SFCM) the tip and/or sample electrode of the STM is moved vertically and laterally so that the power in the MFC may be measured at one or more locations on the surface of the sample and, from the power, carrier density, and other characteristics, of the sample may be calculated. SFCM is non-destructive of the sample. While many systems are possible to practice SFCM, a preferred apparatus is disclosed.

Abstract: A method for coupling high-frequency energy, in particular for microwave circuits, to a nanoscale junction involves placing a bias-T outside of the tip and sample circuits of a scanning probe microscope and connecting a portion of a sample of analyzed semi-conductor through an outer shielding layer of coaxial cable so as to complete a circuit with minimal involvement of the sample. The bias-T branches into high and low-frequency circuits, both of which are completed and, at least the high-frequency circuit, does not rely on grounding of implements or other structure to accomplish said completion.

Abstract: A method for coupling high-frequency energy, in particular for microwave circuits, to a nanoscale junction involves placing a bias-T outside of the tip and sample circuits of a scanning probe microscope and connecting a portion of a sample of analyzed semi-conductor through an outer shielding layer of coaxial cable so as to complete a circuit with minimal involvement of the sample. The bias-T branches into high and low-frequency circuits, both of which are completed and, at least the high-frequency circuit, does not rely on grounding of implements or other structure to accomplish said completion.

Abstract: Apparatus for generating a microwave frequency comb (MFC) in the DC tunneling current of a scanning tunneling microscope (STM) by fast optical rectification, caused by nonlinearity of the DC current vs. voltage curve for the tunneling junction, of regularly-spaced, short pulses of optical radiation from a focused mode-locked, ultrafast laser, directed onto the tunneling junction, is described. Application of the MFC to high resolution dopant profiling in semiconductors is simulated. Application of the MFC to other measurements is described.

Abstract: Field emission devices utilizing capacitive ballasting are described with possible uses in industry. The preferred device utilizes opposing electrodes, each with a dielectric layer and a plurality of conductive islands which serve to exchange electrons, generating an oscillatory current. Ideally these islands are dome-shaped and made of a refractory metal such as tungsten of molybdenum. Through proper use and selection of materials, electrical fields with densities of 1014 A/m2 are capable of being generated.