rus
Issue #3-4/2024
B.A.Loginov,Y.V.Khripunov, M.A.Shcherbina, А.А.Smirnov, А.К.McCoy, N.S.Nekhaenko, P.A.Granatkin, H.Y.Hamdy, N.R.Kalnazarova, E.O.Petryaev, C.K.Tanasa, Х.А.Ahrorova, D.R.Ainulova, M.N.Pluzhnik, A.A.Mizgaylo, V.A.Bobarykina, M.V.Mamikoyan, A.R.Izmailova
DEVELOPMENT OF A METHOD FOR UPDATING THE PROBE OF A SCANNING PROBE MICROSCOPE IN OPEN SPACE CONDITIONS
DEVELOPMENT OF A METHOD FOR UPDATING THE PROBE OF A SCANNING PROBE MICROSCOPE IN OPEN SPACE CONDITIONS
| DOI: https://doi.org/10.22184/1993-8578.2024.17.3-4.166.175
A new method of updating the needle of a scanning probe microscope by sputtering different materials on it has been developed, tested and optimised. Experiments on sputtering different metals on the needle were performed, scans were taken with this needle in a scanning tunnelling microscope before and after sputtering metals on it, and the change in resolving power after sputtering metals as the main parameter of the microscope was evaluated. The new method of probe updating was developed for the world’s first space scanning tunnelling microscope, but it is also applicable for probe microscopes of other types, for example, for atomic force microscopes, as well as for various applications of probe microscopes in general, including those operating in vacuum chambers for various purposes.
A new method of updating the needle of a scanning probe microscope by sputtering different materials on it has been developed, tested and optimised. Experiments on sputtering different metals on the needle were performed, scans were taken with this needle in a scanning tunnelling microscope before and after sputtering metals on it, and the change in resolving power after sputtering metals as the main parameter of the microscope was evaluated. The new method of probe updating was developed for the world’s first space scanning tunnelling microscope, but it is also applicable for probe microscopes of other types, for example, for atomic force microscopes, as well as for various applications of probe microscopes in general, including those operating in vacuum chambers for various purposes.
INTRODUCTION
On 27 June 2023, Russia launched the world’s first [1] satellite scanning probe microscope (SMM-2000C) into space in the Nanozond-1 satellite, which immediately began transmitting frames (https://nauka.tass.ru/nauka/18422659) and has been successfully operating for almost a year (https://www.mos.ru/news/item/136461073). The construction of new similar spacecraft [2] was started for different tasks in space – both for assessing surface resistance of various materials in open space conditions with solar wind ion streams and for assessing the extent of space pollution by micro- and nanosized dust particles arising from the collision of old unguided satellites.
One of the problems of probe microscope operation in an unmanned satellite is microscope probe durability during more than two years of flight. There is very little space for a microscope with its own electronics and processor in a satellite of the now common CubeSat-3U format – no more than 90 × 90 × 200 mm. We have to shrink the dimensions of the microscopes themselves, not to mention the fact that we have to put together with them some probe replacement mechanisms. Therefore, it has become urgent to invent a method of probe renewal that would take up as little space as possible.
The idea came in the process of work on the selection of materials for sputtering in space to cover non-electrically conductive objects with a conductive film [3] for possibility of their study in a satellite scanning tunnelling microscope. This idea consisted in the following: perhaps, when metal is sputtered onto the spent needle of a scanning probe microscope with a blunted point, new nanoneedles will be formed at the end of this point, which will work.
MATERIALS AND METHODS
The choice of metals considered for sputtering to test the idea of the probe upgrade was actually prepared by the above-mentioned previous work [3], where presented the list of metals whose films retain electrical conductivity in the conditions of residual atmospheric gases, where the Earth’s satellite may be. These are such metals as gold, silver, nickel, zinc, bismuth and Wood’s alloy consisting of bismuth (50%), lead (25%), tin (12.5%) and cadmium (12.5%). CVD/PVD deposition methods similar to those described in [4–9] were considered for sputtering. However, in conditions of small volume in the satellite it turned out to be extremely difficult to use plasma, including magnetron, sputtering methods, due to the need to place for their operation a gas cylinder, most often argon, as well as gas supply valves with their control units. Therefore, as in [3], the method of thermoemission sputtering of metal was chosen, which is practically feasible in the satellite, in which it is required to place near the probe heated by current small-sized spiral with a diameter of 2–3 mm and length of 3–5 mm of metal wire, and to supplement the electronic board with only one transistor with dimensions of about 8 × 6 × 2 mm to switch on the electric current through the spiral, as a result of the spiral is heated and from it vaporise metal atoms deposited on the microscope probe.
Two international teams – a team of participants of the World Youth Festival WYF-2024 from 01 to 06 March 2024 (project "The world’s first probe microscope-satellite of the Earth: experiment of probe renewal in open space", https://www.miet.ru/news/162401) and a team of the International Children’s Programme "Global Grand Challenges" GGC-2024 from 08 to 21 March 2024 (project "Development of the procedure of probe renewal of the scanning microscope-satellite", https://www.miet.ru/news/162401) – took part in the development of this method of probe renewal one after another.
The vacuum system used was the "MAG-5 vacuum-plasma unit" (PROTON Plant, Zelenograd, Russia, www.microscopy.su), in which physical (PVD) and chemical (CVD) deposition processes can be realised [4–9]. All experiments were conducted at a pressure of 10–3 mbar, which corresponds to the conditions of open space at an altitude just below the Karman line, the boundary 100 km above the Earth’s sea level between space and atmosphere. This pressure was chosen for the experiments as the most rigid experimental condition – due to presence of impurities in the form of residual atmosphere. For the purpose of correct comparison of metals, their sputtering on probes was carried out with heating of a molybdenum boat, in which pieces of metals were placed, to a temperature at which the rate of vaporisation of metals was approximately the same. Diagram and photos of the sputtering processes together with photos of the co-authors working on it are presented in Fig.1.
To determine the resolving power of the probes, we used a commercially available "Scanning Probe Microscope SMM-2000" (PROTON Plant, Zelenograd, Russia, www.microscopy.su, number 46918 in the State Register of Measuring Instruments of the Russian Federation), the flight version of which works in space and which has a large resolution reserve for this work, up to visualisation of individual atoms. The needles before and after metal sputtering on them in the scanning tunnelling microscopy mode used in space were scanned with the same sample of a gold mirror, the same as the one used in space in this microscope. After that, using the SMM-2000 microscope software, the granulometric analysis was performed, the histogram of distribution statistics of the observed gold particles diameters, which make up the mirror, was built, and the first smallest diameter of these grains, the percentage of which exceeded 1% of their total number, was taken as an answer to the question "what is the resolving power of the probe used at the moment". There were also smaller grains in the distribution, but if they were less than 1% of the total number, they were not taken into consideration to exclude frame noise. Visual determination of the diameter of those very small grains, which, however, are clearly perceived by the eye as a separate independent grain with clear boundaries, was also performed. It should be noted that the work started by the team of the World Youth Festival WYF-2024 was continued by the team "Global Grand Challenges" of GBV-2024, which additionally proposed to make special jamming of probes by contact touching them with a glass plate, emulating the most severe wear of the needle in space as a result of its contact with a mirror due to some event, and also mastered the granulometric analysis of the SMM-2000 microscope programme to determine the resolution of the probe in addition to visual analysis. The results of work on the microscopes and photographs of the co-authors working with the microscopes are presented in Figs.2, 3 and 4.
RESULTS AND DISCUSSION
The result of the conducted researches are shown in the tables of minimum sizes of grains obtained on new needles, as well as on the same needles after metallisation (Table 1) or on the same needles, but before metallisation jammed by impact of the point against glass (Table 2).
It can be seen from Table 1 that the best metal for probe upgrades was gold, giving the best resolution of the gold mirror grains.
From Table 2, it can be seen that in general, for all metals, based on the results of numerical particle size analysis, the probe fully recovers its functionality after metal sputtering even after jamming.
The final conclusion of the research was the decision to start the development of a design providing the above-described developed new method of probe renewal – for its implementation in the next scanning probe microscopes to be launched into space. With the use of gold as a metal, simultaneously sputtered both on the sample to give electrical conductivity to all objects on its surface [3], and on the probe, for its renewal. This choice of gold coincided coincidentally with the use of gold as a mirror material in the space microscope, which is exposed to solar wind ions and on which fast space dust particles are to be stuck for research. It should also be emphasised that the above-described new method of probe upgrade was developed for the world’s first space scanning tunnelling microscope, but it is also applicable to probe microscopes of other types, for example, to common atomic force microscopes, as well as to various applications of probe microscopes in general [10], including those operating in vacuum chambers for various purposes.
ACKNOWLEDGMENTS
This work was carried out thanks to the partnership of the Sirius Educational Centre, JSC PROTON Plant, Zelenograd, National Research University MIET, I.S.Turgenev Oryol State University, Sputniks LLC and the Foundation for Promotion of Innovations, Moscow. The world’s first scanning probe microscope – an Earth satellite – was launched under the Planet Watch programme and further launches are planned.
PEER REVIEW INFO
Editorial board thanks the anonymous reviewer(s) for their contribution to the peer review of this work. It is also grateful for their consent to publish papers on the journal’s website and SEL eLibrary eLIBRARY.RU.
Declaration of Competing Interest. The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
On 27 June 2023, Russia launched the world’s first [1] satellite scanning probe microscope (SMM-2000C) into space in the Nanozond-1 satellite, which immediately began transmitting frames (https://nauka.tass.ru/nauka/18422659) and has been successfully operating for almost a year (https://www.mos.ru/news/item/136461073). The construction of new similar spacecraft [2] was started for different tasks in space – both for assessing surface resistance of various materials in open space conditions with solar wind ion streams and for assessing the extent of space pollution by micro- and nanosized dust particles arising from the collision of old unguided satellites.
One of the problems of probe microscope operation in an unmanned satellite is microscope probe durability during more than two years of flight. There is very little space for a microscope with its own electronics and processor in a satellite of the now common CubeSat-3U format – no more than 90 × 90 × 200 mm. We have to shrink the dimensions of the microscopes themselves, not to mention the fact that we have to put together with them some probe replacement mechanisms. Therefore, it has become urgent to invent a method of probe renewal that would take up as little space as possible.
The idea came in the process of work on the selection of materials for sputtering in space to cover non-electrically conductive objects with a conductive film [3] for possibility of their study in a satellite scanning tunnelling microscope. This idea consisted in the following: perhaps, when metal is sputtered onto the spent needle of a scanning probe microscope with a blunted point, new nanoneedles will be formed at the end of this point, which will work.
MATERIALS AND METHODS
The choice of metals considered for sputtering to test the idea of the probe upgrade was actually prepared by the above-mentioned previous work [3], where presented the list of metals whose films retain electrical conductivity in the conditions of residual atmospheric gases, where the Earth’s satellite may be. These are such metals as gold, silver, nickel, zinc, bismuth and Wood’s alloy consisting of bismuth (50%), lead (25%), tin (12.5%) and cadmium (12.5%). CVD/PVD deposition methods similar to those described in [4–9] were considered for sputtering. However, in conditions of small volume in the satellite it turned out to be extremely difficult to use plasma, including magnetron, sputtering methods, due to the need to place for their operation a gas cylinder, most often argon, as well as gas supply valves with their control units. Therefore, as in [3], the method of thermoemission sputtering of metal was chosen, which is practically feasible in the satellite, in which it is required to place near the probe heated by current small-sized spiral with a diameter of 2–3 mm and length of 3–5 mm of metal wire, and to supplement the electronic board with only one transistor with dimensions of about 8 × 6 × 2 mm to switch on the electric current through the spiral, as a result of the spiral is heated and from it vaporise metal atoms deposited on the microscope probe.
Two international teams – a team of participants of the World Youth Festival WYF-2024 from 01 to 06 March 2024 (project "The world’s first probe microscope-satellite of the Earth: experiment of probe renewal in open space", https://www.miet.ru/news/162401) and a team of the International Children’s Programme "Global Grand Challenges" GGC-2024 from 08 to 21 March 2024 (project "Development of the procedure of probe renewal of the scanning microscope-satellite", https://www.miet.ru/news/162401) – took part in the development of this method of probe renewal one after another.
The vacuum system used was the "MAG-5 vacuum-plasma unit" (PROTON Plant, Zelenograd, Russia, www.microscopy.su), in which physical (PVD) and chemical (CVD) deposition processes can be realised [4–9]. All experiments were conducted at a pressure of 10–3 mbar, which corresponds to the conditions of open space at an altitude just below the Karman line, the boundary 100 km above the Earth’s sea level between space and atmosphere. This pressure was chosen for the experiments as the most rigid experimental condition – due to presence of impurities in the form of residual atmosphere. For the purpose of correct comparison of metals, their sputtering on probes was carried out with heating of a molybdenum boat, in which pieces of metals were placed, to a temperature at which the rate of vaporisation of metals was approximately the same. Diagram and photos of the sputtering processes together with photos of the co-authors working on it are presented in Fig.1.
To determine the resolving power of the probes, we used a commercially available "Scanning Probe Microscope SMM-2000" (PROTON Plant, Zelenograd, Russia, www.microscopy.su, number 46918 in the State Register of Measuring Instruments of the Russian Federation), the flight version of which works in space and which has a large resolution reserve for this work, up to visualisation of individual atoms. The needles before and after metal sputtering on them in the scanning tunnelling microscopy mode used in space were scanned with the same sample of a gold mirror, the same as the one used in space in this microscope. After that, using the SMM-2000 microscope software, the granulometric analysis was performed, the histogram of distribution statistics of the observed gold particles diameters, which make up the mirror, was built, and the first smallest diameter of these grains, the percentage of which exceeded 1% of their total number, was taken as an answer to the question "what is the resolving power of the probe used at the moment". There were also smaller grains in the distribution, but if they were less than 1% of the total number, they were not taken into consideration to exclude frame noise. Visual determination of the diameter of those very small grains, which, however, are clearly perceived by the eye as a separate independent grain with clear boundaries, was also performed. It should be noted that the work started by the team of the World Youth Festival WYF-2024 was continued by the team "Global Grand Challenges" of GBV-2024, which additionally proposed to make special jamming of probes by contact touching them with a glass plate, emulating the most severe wear of the needle in space as a result of its contact with a mirror due to some event, and also mastered the granulometric analysis of the SMM-2000 microscope programme to determine the resolution of the probe in addition to visual analysis. The results of work on the microscopes and photographs of the co-authors working with the microscopes are presented in Figs.2, 3 and 4.
RESULTS AND DISCUSSION
The result of the conducted researches are shown in the tables of minimum sizes of grains obtained on new needles, as well as on the same needles after metallisation (Table 1) or on the same needles, but before metallisation jammed by impact of the point against glass (Table 2).
It can be seen from Table 1 that the best metal for probe upgrades was gold, giving the best resolution of the gold mirror grains.
From Table 2, it can be seen that in general, for all metals, based on the results of numerical particle size analysis, the probe fully recovers its functionality after metal sputtering even after jamming.
The final conclusion of the research was the decision to start the development of a design providing the above-described developed new method of probe renewal – for its implementation in the next scanning probe microscopes to be launched into space. With the use of gold as a metal, simultaneously sputtered both on the sample to give electrical conductivity to all objects on its surface [3], and on the probe, for its renewal. This choice of gold coincided coincidentally with the use of gold as a mirror material in the space microscope, which is exposed to solar wind ions and on which fast space dust particles are to be stuck for research. It should also be emphasised that the above-described new method of probe upgrade was developed for the world’s first space scanning tunnelling microscope, but it is also applicable to probe microscopes of other types, for example, to common atomic force microscopes, as well as to various applications of probe microscopes in general [10], including those operating in vacuum chambers for various purposes.
ACKNOWLEDGMENTS
This work was carried out thanks to the partnership of the Sirius Educational Centre, JSC PROTON Plant, Zelenograd, National Research University MIET, I.S.Turgenev Oryol State University, Sputniks LLC and the Foundation for Promotion of Innovations, Moscow. The world’s first scanning probe microscope – an Earth satellite – was launched under the Planet Watch programme and further launches are planned.
PEER REVIEW INFO
Editorial board thanks the anonymous reviewer(s) for their contribution to the peer review of this work. It is also grateful for their consent to publish papers on the journal’s website and SEL eLibrary eLIBRARY.RU.
Declaration of Competing Interest. The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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