Electronics of the device Solver-P47

1.Entering amplifiers. In the STM mode two entering amplifiers are used: on a range of entering currents 10pA - 10nA and 1pA - 1nA in work in a mode Z-const. They are converters a current - voltage with trans impedance 20MoHm and 200MoHm accordingly. Value of an entering current 50 and 5 nA, frequency band - 15 and 6 kHz accordingly. In a AFM mode the entering amplifier represents quarter converter a photocurrent - voltage (on one on each section of the photoreceiver) with a band 1 MHz) .On summing - subtracting amplifiers the scheme converting 4 entering signals in voltage that is proportional to normal deviation of cantilever, lateral turn and full background of the photoreceiver is assembled. Last is used for maintaining of a constant relative deviation of cantilever, that allows to compensate instability and noise of the laser even in the work with a nonzero difference signal. 2. Entering filters. For work in a condition of modulation techniques and also for a diminution of entering noise some filters are used. In the STM mode it is a low-pass filter of the 3-rd degree with a band 10kHz permitting to support a constant average current in work with a measurement dI/dZ or dI/dU with modulation Z or U on frequency above 18 kHz. For selection modulated signal the bandpass filter of the 5-th degree on frequency 18 - 25 kHz is used. In AFM mode it is two interfaced filters 3-rd degree of the upper and lower frequencies with a frequency of a shear 50 kHz. As an entering signal the signal gived on the entering exterior connector of a device can be used. The parameters of its filters are identical to filters of the channel AFM. 3. Multiplexes and converters of signals. In the device three groups of multiplexes are used: multiplexes - amplifiers of entering signals permitting to select from entering signals (low-frequency and band STM, low-frequency and high-frequency AFM and exterior) signals subjected to transformation. Multiplexes choosing two independent signals for a simultaneous measurement by two ADC. Multiplexes choosing an output signal for use in a circuit of a feed-back in the work of maintaining of a constant entering current, amplitude of modulation etc. The converters of signals allow simultaneously and independently to receive a signal that is proportional to log of an entering current, and also, in the work in modulation mode, signal proportional to amplitude of entering (with use of synchronous detecting), root-mean-square magnitude entering, shift of a phase between entering and energizing signals. All signals pass through controlled pass filters of the low frequencies of 2-nd degree with a range of reorganization 200Hz - 20kHz. Frequency range in work with modulation techniques - in STM mode:18 - 25kHz, in AFM mode: 1kHz - 1.8 MHz in studying of cantilever properties and 50 kHz - 1.2 MHz in scanning of a surface of a sample. The synchronous detecting is possible for using on frequencies that are multiple to driving frequency. The operational mode with maintaining of a constant shift of a phase between energizing and entering signals is possible due to modification of the oscillating cantilever's frequency by a circuit of a feed-back. In using of conducting cantilevers it is possible to maintain one from its oscillating parameters (phase, amplitude, etc.) by modification of a potential given on cantilever. 4. The circuit of a feed-back consists of the scaling amplifier, polarity control, integrator with a controlled constant of time and both conditions of a dumping and storage, error amplifier, multiplying 16-digit DAC of maintaining assigning a level of a feed-back signal. As a basic voltage of this DAC the signal proportional to full flesh of the photoreceiver can be used, that, as has already been marked, reduces the sensitivity of a device to instability and noise of the laser. 5. 16-digit ADC. Two 16-digit ADC allow simultaneously to register two various signals independently selected from a set of all entering, transformed and exterior signals. Before each ADC the low-pass filter of the 2-nd degree rebuilt in a range 100Hz-20kHz is located. Before one ADC there are the 16-digit DAC of a displacement and differential amplifier permitting to compensate a constant component of measuring signal and also controlled amplifier with an amplification gain 1,10,100,1000. It allows to increase an ADC resolution up to a level stipulated by entering noise in a stripe of measurement. 6. The amplifiers X and Y for piezoscanner deviation are identical and represent a composite DAC and high-voltage amplifier with a paraphase exit. It increases a full range of voltage on piezoscann up to + 320V/-320V in unipolar feed 350V. A stripe of amplifiers X and Y 2.5kHz. The composite DAC consists of two precision 16- digit DACs, precision radiant basic, two deglichers (for suppression of ejections in switching of DACs). The use of various amplification gains for DACs allows to reach effective word length of composite DAC - 22 binary bits, that on a field 100 X 100 mkm should give a minimum pitch 0.025 nm. The problem of the exact coordination of two DACs amplification is eliminated by that the scanning always is made only one from them: by "higher" or "junior" - dependently on selected magnitude of a scanning field. The amplifier Z of piezoscann deviation contains the similar scheme of composite DAC, but the high-voltage amplifier has one exit (0-320V), more wider stripe - 15 kHz, and is capable to work on a load up to 100nF. It has input of extern modulation and possibility of feeding of an input modulating signal. Resistance devider and buffer amplifier serve for a measurement of volume Z in the mode with a live feed-back on Z. 7. The block of frequencies synthesis consists of three 32 digit independent synthesizers of signals sin (wt), cos (wt) - for synchronous detecting and cos (wt+) - for modulating actions. Frequency, amplitude and phase are rebuilt independently. A step of reorganization on frequency - 0.01 Hz, on a phase - 0.1°. The amplitude of modulating action can vary in a range 1mV-10V with step 1mV. As the setting device of basic frequency can be selected or quartz generator (40 MHz), or in the feed-back mode on a phase and control by frequency, VCG (9-11 MHz). 8. The control unit of approach consists of two 12- digit DAC, programmable to make two shifted on 90° sinusoidal voltages impressed on two power amplifiers controlling current through windings of approach step engine. 9. The stabilizer of temperature allows to support a constant temperature of a wafer with a sample in a range 30 - 120°C with an accuracy 0.05°.