JPH10311794A - Scanning emission microscope - Google Patents

Abstract

(57) [Summary] [Problem] To provide a scanning light emitting microscope capable of measuring a high-quality weak light image without impairing the scanning speed of a probe by adding a function to the scanning probe microscope additionally. The purpose is to do. A light for injecting charged particles or projected light from a probe to a sample, detecting light generated by the injected charged particles or the projected light, and outputting a pulse signal corresponding to the light. In a scanning light emitting microscope having a detector 4 and an integrator 6 for integrating the number of the pulse signals, starting or stopping the operation of integrating the pulse signals is performed by:
The signal line 7 composed of a single line is controlled, and the reading or erasing of the accumulation result of the pulse signal is controlled by the signal line 8 composed of a single line, and the accumulation result is output as integrated data as digital data. Terminal 10
Output from a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the characteristics of a minute area of a sample by detecting light emission generated by injecting charged particles or photons from a probe into a minute area on the surface or inside of the sample by a photon counting method. The present invention relates to a scanning light emission microscope used for evaluation.

[0002]

2. Description of the Related Art With the progress of crystal growth technology and microfabrication technology,
Research and development of nanometer-sized quantum devices and quantum structures have been vigorously pursued due to expectations for new functions due to quantum effects. To improve the performance of these devices and structures,
There is a strong demand to measure the electronic and optical characteristics of a minute area with high spatial resolution.

[0003] In recent years, by utilizing light (near-field light) or local light emission (luminescence) generated by electrons (tunnel electrons) injected into a sample from a probe, the electronic characteristics and optical characteristics of a minute region are reduced to a nanometer level. Apparatuses have been developed to evaluate at a spatial resolution of "Reference: For example, TM
urashita, J.A. Vac. Sci. Technol. B15, 32
(1997). ". Although this type of device has various names depending on the type of light or charged particles to be injected, these devices will be collectively referred to as a scanning emission microscope in the text.

The scanning probe microscope ST
Although M and AFM have become widespread, there has been a strong demand to add an optical measurement function to these and reconfigure the scanning emission microscope. Scanning light-emitting microscopes measure light detection signals in conjunction with probe scanning, but the amount of light detected is usually as low as tens of thousands of counts / second, and the output of the detector is the time corresponding to the arrival of each photon. It becomes a pulse train that is discrete in nature. Therefore, a method of integrating the number of photons is used for the light quantity measurement. This is known as the photon counting method (photon counting method). There is a long-awaited demand for a photon number integrating means capable of measuring a high-quality detected light image by additionally providing such a measuring means in a scanning probe microscope.

A digital output conventionally used as an integrator applied to the photon counting method (hereinafter referred to as a digital integrator in the text) is applied to a high-speed detection light image measurement interlocked with probe scanning. Is not taken into account, and it is connected to the control computer with a general-purpose data interface (GPIB),
An operation such as integration of the number of pulses is performed in accordance with a command command from the control computer, and the result of the integration is returned to the control computer through the GPIB.

[0006]

However, such a conventional scanning emission microscope has the advantage that the configuration using the GPIB allows the apparatus configuration to be flexible, but follows the scanning because the data transfer speed is low. There was a disadvantage that it could not be done. Further, since all controls are received in the form of commands from a computer, if an attempt is made to configure a scanning emission microscope by additionally configuring the existing scanning probe microscope,
There is a problem that the control circuit becomes complicated and the configuration becomes difficult.

Therefore, as a method capable of performing a high-speed measurement to some extent, a photon number integrator (hereinafter, referred to as a rate meter in the text) which outputs an analog voltage proportional to the integration result using a digital-to-analog (DA) converter. Is additionally attached to a scanning probe microscope. This rate meter has a function of constantly outputting the result of integrating the number of photons with a constant time constant as an analog voltage asynchronously with scanning. A method has been used in which this analog voltage is transferred to a reading device via a coaxial cable and converted into digital data by an analog-to-digital (AD) converter of the reading device. In this method, an existing scanning probe microscope can be used if only an AD converter is used, so that the configuration is easy. However, since the response speed cannot be so fast, the rate meter has problems such as waveform distortion and level fluctuation of the output signal due to the restriction of the response speed, which deteriorates the image quality. However, there is a problem that large fluctuations remain on the image.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and a high-quality faint light image measurement without impairing the scanning speed of a probe can be achieved by adding a function to a scanning probe microscope. It is an object of the present invention to provide a scanning light-emitting microscope that enables the following.

[0009]

According to the present invention, in order to achieve this object, a scanning probe microscope having a probe and a control device for injecting charged particles or projected light into a sample is provided. In a scanning light emission microscope having a light detector that detects light generated by the particles or the projection light and outputs a pulse signal corresponding to the detected light, and an integrator that integrates the number of the pulse signals, The start or stop of the pulse signal integration operation is
Controlling by a signal that can be propagated by a first signal line composed of a single line, and controlling reading or erasing of the integration result of the pulse signal by a signal that can be propagated by a second signal line composed of a single line; The integration result is transmitted to the scanning probe microscope.

[0010]

FIG. 1 is a block diagram showing a scanning light emitting microscope according to the present invention. As shown in the figure, the probe 2 is caused to scan on the measurement sample 1 by the probe scanning signal 11 output from the control circuit 12 of the scanning probe microscope 13. The light 3 emitted from the sample 1 by the charged particles or the projected light injected from the probe 2 is detected by a photodetector 4 (for example, a photomultiplier), and a discriminator (waveform shaping) in the photodetector 4 is formed. ) To form rectangular pulses corresponding to individual photons. The output terminal of the discriminator 4a and the integrator 6 are connected by the coaxial cable 5, and the discriminator 4a
The rectangular pulse output from the above enters the pulse input terminal 5a of the integrator 6.

The integrator 6 has a photon pulse input terminal 5a and an integrated data output terminal 10a as signal input / output terminals, and S / S (start / stop) as an operation control terminal.
Two control terminals 7a and an R / C (data read / data clear) control terminal 8a are provided. Where S
The / S control terminal 7a, the R / C control terminal 8a, and the pulse input terminal 5a are BNC connectors for connecting coaxial cables, and the integrated data output terminal 10a is a parallel connector.
Interface. These terminals are connected to the scanning probe microscope 13 via a predetermined connection cable.
In the present invention, the operation is exactly the same even if the data length of the parallel interface is appropriately increased or decreased according to the range of the number of pulses to be integrated. If the data length is short, a high-speed integrator 6 can be configured at a lower cost. The integrator 6 has a function of integrating the number of pulses and a temporary memory 9 for storing the integration result.

S / S control terminal 7a and R / C control terminal 8a
Are connected to the scanning probe microscope 13 by coaxial cables. The S / S control terminal 7a receives a control pulse for instructing the start timing of the integration operation of the integrator 6 and a control pulse for instructing the end time of the operation. From the scanning probe microscope 13. The R / C control terminal 8a is provided with a control pulse for instructing the timing of outputting the data of the integration result and a control pulse for instructing the timing of erasing the data of the integration result from the temporary memory 9 of the integrator 6, respectively. Are transmitted from the scanning probe microscope 13 as signals that can be propagated by the signal line (single line) 8. The data of the integration result of the integrator 6 is output as digital data from the parallel interface (integration data output terminal 10a) and transmitted to the scanning probe microscope 13.

An image to be measured is composed of a large number of pixels. In image measurement, the measuring operation is repeated for each pixel. Therefore, the operation of the present invention at an arbitrary pixel on an image will be described below. The operation is the same for other pixels.

FIG. 2 is a diagram showing an operation procedure of the present invention. As shown in the figure, first, the probe moves from the immediately preceding pixel to the pixel to be measured, and the position control of the probe and the feedback control of tunneling electrons are performed within a fixed time, so that the probe position and the tunnel current are stabilized. (A). Here, a control signal (data erasure signal) is sent from the scanning probe microscope 13 to the R / C control terminal 8 a of the integrator 6. Upon receiving this data erasure signal, the integrator 6 erases the data of the integration result stored in the temporary memory 9 (b). Thereafter, the scanning probe microscope 13 sends the S / S control terminal 7 of the integrator 6
A control pulse (start signal) for starting integration is sent to a.
Upon receiving this start signal, the integrator 6 starts integrating the number of pulses input to the pulse input terminal 5a (c).
When the designated time has elapsed, a control pulse (stop signal) is sent again to the S / S control terminal 7a, and when the integrator 6 receives the stop signal, the integration operation is stopped and the integration is terminated (d). The integration result is read as digital data in the integrator 6 and stored in the temporary memory 9. Here, the case where the stop signal is transmitted from the scanning probe microscope 13 to the integrator 6 has been described. However, a timer is provided in the integrator 6 and the measurement time after receiving the start signal is measured by the timer. There is also a method of generating a stop signal inside the integrator 6.

Next, from the scanning probe microscope 13
A control signal (data read signal) is sent to the C control terminal 8a. Upon receiving the data read signal, the integrator 6 sends the data of the integration result stored in the temporary memory 9 to the reading circuit in the control circuit 12 of the scanning probe microscope 13 (e). When the reading of the data is completed, the scanning probe microscope 13 moves the probe to the position of the next pixel, and repeats the above operation again (f).

Here, a case has been described in which the data erasure is performed by sending a data erasure signal before the start of the integration, but the data erasure operation can be performed inside the integrator 6 a fixed time after the data read signal is received. There is also a procedure for erasing data immediately after receiving a start signal and thereafter starting an integrating operation. In this case, the start signal also serves as the data erasure signal, and the operation of individually sending the data erasure signal from the scanning probe microscope 13 to the integrator 6 can be omitted. It is of course possible to erase data after the data reading operation.

As described above, since the integration operation and the data transfer are controlled only through the two first signal lines 7 and the second signal lines 8 from the scanning probe microscope 13,
It can be easily and economically added to the scanning probe microscope 13, and can perform optical image measurement completely synchronized with high-speed probe scanning. In addition, since the data of the integration result is deleted and updated in each pixel, it is possible to prevent the result of the previous pixel from affecting the next pixel, and to obtain a high-quality optical image.

Since the present invention employs the above-described means and method, a scanning light-emitting microscope capable of measuring a high-quality detection light image in synchronization with high-speed probe scanning can be realized.

[0019]

As described above, the scanning light-emitting microscope according to the present invention has a simple apparatus configuration and requires only two single wires, so that it is economical to use a conventional scanning probe microscope. By adding an integrator, it is possible to configure a scanning emission microscope that obtains a high-quality photon count image synchronized with high-speed scanning.

The present apparatus can be added to not only a scanning probe microscope but also general apparatuses that require image measurement of weak light, such as a computer tomography apparatus (CT scanner) and a cathodoluminescence microscope.
It has a wide range of applications and exhibits excellent versatility, flexibility, functionality and usefulness.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a scanning emission microscope according to the present invention.

FIG. 2 is a diagram illustrating an operation procedure of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Measurement sample 2 ... Probe 3 ... Light 4 ... Photodetector 4a ... Discriminator 5 ... Coaxial cable 5a ... Pulse input terminal 6 ... Integrator 7 ... 1st signal line (single line) 7a ... S / S control Signal terminal 8: Second signal line (single line) 8a: R / C control signal terminal 9: Temporary memory 10: Integration data 10a: Integration data output terminal 11: Probe scanning signal 12: Control circuit 13: Scanning probe microscope

Claims (1)

[Claims] A scanning probe microscope having a probe and a control device for injecting charged particles or projected light into a sample, detecting light generated by the injected charged particles or projected light, and detecting the detected light. In a scanning light emitting microscope having a photodetector that outputs a pulse signal corresponding to light and an integrator that integrates the number of the pulse signals, the start or stop of the operation of integrating the pulse signal is performed by a single line. The readout or erasure of the integration result of the pulse signal is controlled by a signal that can be propagated by a second signal line composed of a single line, and the integration result is scanned by the signal that can be propagated by one signal line. A scanning light-emitting microscope characterized by transmission to a scanning probe microscope.