Учебно-методическое пособие для студентов старших курсов Издательство мгту им. Н. Э. Баумана 2009 Редактор кандидат филологических наук
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Grammar exercises Exercise 1. Translate the following sentences paying attention to Participle Constructions in different syntactic functions.
Exercise 2. Point out Adverbial Participle constructions and Absolute Participle constructions in the following sentences, translate them accordingly.
LESSON 3 Memorize the following basic vocabulary and terminology to text 3A
Read text 3A and answer the questions after the text Text 3A AlGaN/GaN heterojunction for Hall Effect sensors Hall effect sensors are widely used as proximity switches, position sensors, velocity sensors, and in current sensing applications. Although it is one of the best known solid-state devices, the Hall effect sensor is still attracting considerable attention. One of the areas of interest is to enable Hall effect sensors to function at high temperatures (>250 °C) and other harsh environmental conditions; those operating conditions are of prime importance for a wide range of industrial and military applications. Conventional Hall effect sensors are mainly based on silicon or compound semiconductors, such as InAs, InSb, and GaAs. The advantage of using silicon as the active layer of a Hall effect sensor is its easy integration with signal-conditioning circuits and its low cost. InAs, InSb, GaAs, and related heterojunctions typically have very high electron mobilities. As a result, Hall effect sensors based on these materials can have fairly high magnetic field sensitivity at low temperature up to room temperature. However, due to the narrow band gap of these materials, thermal activation of intrinsic carriers can significantly change their transport properties at higher temperature (>200 °C). The resulting large temperature cross sensitivity makes these sensors unusable at temperatures above approximately 200 °C. By heavily doping the active layer, the extrinsic state of these semiconductors may be maintained to somewhat elevated temperatures; however, due to a sacrifice in carrier mobility, this approach is quite limited. Currently most Hall effect sensors on the market have a peak specified operation temperature of 200 °C or lower. AlGaN/GaN heterostructures have been a subject of intense investigation recently due to their high potential to be used for high temperature, high power radio frequency (rf) electronics. The wide band gap of GaN-related materials leads to low intrinsic carrier concentration and high breakdown voltage, which is a requirement for extremely high microwave or millimeter wave power applications. Further contributing to the outstanding performance of AlGaN/GaN-based heterojunction transistors is their ability to form a two-dimensional electron gas (2DEG) with sheet carrier densities of 1013 cm−2 or higher near the interface without intentional doping. This is well in excess of those achievable in most other III-V material systems. It has been demonstrated previously that the spontaneous and piezoelectric polarizations play an important role on the 2DEG formation and confinement at the AlGaN/GaN interface. The AlGaN/GaN heterojunction structures were grown by metal organic chemical vapor deposition on sapphire substrates. The epitaxial layer consisted of a 2 μm undoped GaN buffer layer and a 25 nm Al0.3Ga0.7N barrier layer. A sheet resistance of 250 Ohm/sq was obtained from Leighton measurement at room temperature. A capacitance voltage profile showed a 2DEG at the junction interface and no residual charge was found in the AlGaN barrier or the GaN/sapphire interface. Square-shaped Hall devices were defined by optical photolithography followed by mesa etching using an inductively coupled plasma reactive ion etching system in a chlorine-based plasma. Ti/Al/Mo/Au Ohmic contacts were deposited by electron beam evaporation and annealed at 800 °C for 1 min. The processed wafer was diced into 3x3 mm2 chips. Each chip was mounted on top of a resistive heater element using high temperature epoxy. The combined assembly was mounted onto a chip carrier for testing. The heater element was used to raise and maintain the surface temperature of the Hall sensor and was calibrated using a high-precision infrared camera. The output Hall voltage of the AlGaN/GaN Hall effect sensor as a function of temperature and magnetic induction curves have good linearity and are very close to one another from room temperature up to 300 °C. With increasing temperature, no degradation of functionality of the sensor is observed. In fact, the Hall voltage is larger at higher temperatures, which is shown by the larger slope at higher temperatures. As the measurements suggest, 300 °C is not a limiting temperature for operation. The magnetic induction and biasing current were fixed at 1.7 kG and 3 mA, respectively. The current-related magnetic sensitivity increases from approximately 54.5 to 56.5 V/(A*T) between room temperature (RT) and 300 °C. Using a linear regression fitting technique, the temperature coefficient of magnetic sensitivity is calculated to be 103 parts per million (ppm)/°C. This is an excellent value even for conventional Hall effect sensors made for low temperature operation. (3997) Read text 3B and translate the text Text 3B CoFe/AlOx- nanolayers for magnetic tunnelling transistors Recently, many researchers have investigated spin valve structures with nano-oxide layers (NOLs) or specular spin valves (SSVs) in the current-in-plane (CIP) configuration. But they have found many serious problems in achieving a sufficient quality for read head device applications with a density of over 300 Gbit in−2. In these structures, the giant magneto-resistance (GMR) sensitively depends on either the thickness of the free, pinned and spacer layers or the mean free path (MFP) of the electrons. Generally, in a spin valve majority carrier electrons with a long MFP can travel with low resistance through a multilayer in which an applied magnetic field aligns the magnetization of adjacent layers. Moreover, if a NOL is inserted on top of the pinned layer to enhance the GMR effect in the SSVs, which induces more frequent scattering, then the magneto-resistance (MR) ratio is seriously degenerated at high temperatures (>250 C). Thus, there has been a lot of effort made to get rid of this problem by using a current perpendicular-to-plane (CPP) configuration in many different structures, such as magnetic tunnelling junctions (MTJs), spin-valve transistors (SVTs), magnetic tunnelling transistors (MTTs) and organic spin valves. The CPP configuration is expected to solve most of the problems because electrons cross all magnetic layers, whereas in the CIP configuration the MR is diminished by shunting and channelling, and diffusive surface scattering also reduces the MR ratio. Previous studies of MTT structures have revealed a number of factors affecting the characteristics of a device, such as collector current IC, the transfer ratio α (which is defined as α = IC/IE, where IE is emitter current), emitter and collector Schottky barrier heights, the choices of material for the nonmagnetic layers, and the thicknesses of the nonmagnetic layers. In MTTs, the transfer ratio strongly depends on electron transmission at the metal/semiconductor surface. The Schottky barrier height is thought to be an important factor in the determination of the electron transmission coefficient at the interface. The difference in the transfer ratio is due to different scattering mechanisms in the base, wherein the spin-dependent scattering can be attributed to bulk and interface scattering. Thereby, we can enhance the transfer ratio without affecting the relative change in the collector current, because a small change in the collector barrier height increases the chance of collecting both spin-up and spin-down electrons equally (only if we consider the MTT structures containing ferromagnetic layers but not half-metals). Some parameters, such as choice of material for a nonmagnetic layer, thickness of a non-magnetic layer, change in collector current (ΔIC = ICP − ICAP) (where ICP and ICAP are the collector currents in parallel and anti-parallel configurations, respectively) at a certain thickness of the magnetic layers, a domain wall in the junction area, interfacial and barrier spin scattering, and direct coupling between two ferromagnetic layers, have to be optimized for the purpose of applications. Another important parameter is the magneto-current (MC) ratio, which can be expressed by (ICP − ICAP)/ICAP. The MC ratio is sensitive to the mean free path asymmetry of majority and minority electrons. So far, the MC value is not really high enough for applications to read head elements with a density of over 300 Gbit in−2. Besides, the role of order/disorder in the barrier, electrodes, ferromagnetic/insulator interfaces (FM/I), the dependence of voltage and tunnel magneto-resistance (TMR) value, and their TMR are inadequately understood. Neither is the theoretical understanding of the temperature dependence of tunnelling conductance of Al2O3 insulators complete. Nonetheless, for the case of amorphous barriers, all the results have been interpreted successfully. The magnetic tunnelling transistors (MTTs), which have the substrate/CoFe /AlOx (3,5 nm) /CoFe(6 nm) /FeMn(20 nm) /Cu(10 nm) /Ta(5 nm) structures, were prepared at room temperature by direct current (dc) and radio frequency (rf) magnetron sputtering onto Si(100) /SiO2 (150 nm) substrate. Here, we used the targets of Ta, Cu, CoFe and FeMn, where CoFe and FeMn stand for Co90Fe10 and Fe50Mn50, respectively. The collectors of the MTTs were of prime grade P2O5-doped n-Si (50 Ohm*cm) substrates. The background vacuum was better than 10−3 Pa. A native oxide layer on the n-Si surface was removed in a dilute HF solution prior to deposition. Three different metal shadow masks were utilized to form the ferromagnetic base layer (CoFe), the tunnel barrier (AlOx) and the emitter (CoFe /FeMn /Cu/Ta) of each MTT. The base layer thickness was varied from 3 nm to 8 nm. The ohmic contacts to the n-Si substrate were made with thin Pt and thick Al layers, and the largest device dimension is 10 × 12 mm2. The magnetic moment of the CoFe emitter was pinned by an antiferromagnetic FeMn layer, and it could be switched on and off by an external magnetic field of ±800 Oe. The properties of the transistor were measured with an emitter–base bias voltage range of less than 2.5 V. While the emitter–base voltage (VEB) was maintained at zero, the emitter–base current (IEB or IE) and the base–collector current (IBC or IC) were measured as a function of applied magnetic field. The Si-based MTT structures were fabricated using a magnetron sputtering deposition system. MC ratios of 48.3–55.9% for VEB of 1.45–2.0 V, and transfer ratios of (1.3–2.0) ×10−4 for VEB of 1.8–2.0 V were obtained in the MTT structures with differing base thicknesses of 3–8 nm at 77 K. MC ratios of 6.5% and 7.8% were obtained at room temperature (RT) for bias voltages of 2.3 and 2.5 V, respectively. A low MC ratio is closely related to a high leakage current and is due to the decrease in mean free path asymmetry of majority and minority electrons as well as the decrease in PE at room temperature. TMR measurement was also carried out at 77 K and RT. Moreover, the origin of the decrease in mean free path of majority electrons in a thin base and interface state between the Si substrate and CoFe base layer could be clarified by the depth profiles analysis of XPS spectra in the Al2O3(3,5 nm) /CoFe(8 nm) /Si(150 nm) structure. Moreover, the (Co2Si, Fe) intermediate region, formed at the CoFe/Si interface, may have caused the decrease in the value of majority electrons. Therefore, by reducing the leakage current, operation of Si-based MTT structures with an MC ratio of over 53.9% will be realized at RT; this is a good candidate for a new read head device for 300 Gbit in−2 that goes beyond the specular spin valve structures. (5685) Task 1. Give titles to each paragraph of the text. Task 2. Write an abstract and a summary (see example on page 52). Grammar exercises Exercise 1. Analyze the following sentences. Point out clauses in their structure, specify the types of the clauses and translate them.
Texts for rendering in English Text 1 Наноэлектроника является новой областью науки и техники, формирующейся сегодня на основе последних достижений физики твердого тела, квантовой электроники, физической химии и технологии полупроводниковой электроники. Ее содержание определяется необходимостью установления фундаментальных закономерностей, определяющих физико-химические особенности формирования наноразмерных структур (структур с размером от единиц до десятков нанометров, 1 нм = 10~9м), их электронные и оптические свойства. Исследования в области наноэлектроники важны для разработки новых принципов, а вместе с ними и нового поколения сверхминиатюрных супербыстродействующих систем обработки информации. Text 2 С позиций квантовой механики электрон может быть представлен волной, описываемой соответствующей волновой функцией. Распространение этой волны в наноразмерных твердотельных структурах контролируется эффектами, связанными с квантовым ограничением, интерференцией и возможностью туннелирования через потенциальные барьеры. Волна, соответствующая свободному электрону в твердом теле, может беспрепятственно распространяться в любом направлении. Ситуация кардинально меняется, когда электрон попадает в твердотельную структуру, размер которой L, по крайней мере в одном направлении, ограничен и по своей величине сравним с длиной электронной волны. Классическим аналогом такой структуры является струна с жестко закрепленными концами. Колебания струны могут происходить только в режиме стоячих волн с длиной волны Xn = 2L/n, n= 1, 2, 3,... Квантовое ограничение, проявляясь в нанораз-мерных структурах, накладывает специфический отпечаток и на туннелирование. Так, квантование энергетических состояний электронов в очень тонких, периодически расположенных потенциальных ямах приводит к тому, что туннелирование через них приобретает резонансный характер, то есть тун-нельно просочиться через такую структуру могут лишь электроны с определенной энергией. Text 3 Оптическая литография является важнейшей технологией в индустрии полупроводников. Однако для изготовления полупроводниковых элементов с размерами меньше 100 нм требуется ультрафиолетовое излучение с более короткой длины волны. По ряду причин осуществление такого способа вызывает большие затруднения. Электронно-лучевая и рентгеновская литография, которые обсуждались в предыдущих главах, могут быть использованы для получения наноструктур, но с помощью этих процессов не удается достичь высокой производительности, необходимой для крупномасштабного производства. Электронно-лучевая литография использует хорошо сфокусированный электронный пучок, которым наносят заданный рисунок на поверхность материала. С ее помощью можно создавать на поверхности различные структуры с 10-нанометровым разрешением. Так как лучу при этом приходится действовать на поверхность последовательно, от точки к точке, он не может создавать структуры с высокой скоростью, требуемой при конвейерном производстве. Рентгеновская литография дает возможность получать рисунки на поверхности с разрешением 20 нм, но ее технологии, использующие высокоточные маски - трафареты и облучающие системы, сложны и дороги для практического применения. (1070) Text 4 Совсем недавно была разработана методика, называемая нанолитографией, которая может лечь в основу дешевой, высокопроизводительной производственной технологии. Она формирует рисунок на резисте его механическим деформированием с помошью трафарета, несущего изображение наноструктуры, а не модификацией поверхности излучением, как в традиционной литографии. Такой резист - это покрытие, достаточно мягкое для того, чтобы можно было нанести на него отпечаток более твердым штампом. Схема процесса изображена на рис. 13.3. Трафарет с изображением наноструктуры вдавливается в тонкий слой резиста, покрывающего подложку, создавая контрастное изображение на слое. После того как трафарет убран, для удаления оставшегося материала слоя в сжатых областях используется химическое травление. Резист — термопластичный полимер, размягчающийся при нагревании. Для размягчения его обычно нагревают выше температуры стеклования в процессе формирования изображения, облегчая точное воспроизведение шаблона. Трафаретом может быть штамп, изготовленный из металла, диэлектрика или полупроводника методами высокоточной литографии. Нанолитография может создавать изображения на поверхности с разрешением 10 нм по низкой цене и с высокой скоростью, поскольку она не требует использования сложного облучающего оборудования. (1145) Supplementary text Task 1. Read and translate the following text with a dictionary. Task 2. Explain the main principles of the STM design using illustrations. Designing an Air Scanning Tunneling Microscope to Study Two-Dimensional Materials 1. Introduction The scanning tunneling microscope (STM) has developed into an imaging method with diverse possibilities for real-space imaging on a scale that extends to atomic dimensions. The interaction that is monitored in STM is the tunneling current between a metallic tip and a conducting substrate, which are in very close proximity but not actually in physical contact. It is quantum mechanical tunneling that permits the electrons to tunnel through the potential barrier, which they could not surmount according to the classical laws of physics. In this model, the probability of tunneling is exponentially dependent upon the distance of separation between the tip and surface: the tunneling current is therefore a very sensitive probe of this separation. Another great advantage of a STM is that it may allow the characterization and identification of individual atoms and may lead to the manipulation of materials at the atomic scale. One of the principal reasons for building this air STM is to be able to study two-dimensional materials such as graphene and T1S2. Due to the electronic properties of these materials it has been of great interest to explore their use in electronic device applications such as FETs. Because of the reactivity that many surfaces, such as Si have in ambient conditions, the use of an ultra-high vacuum (UHV) system with pressures <10-9torr is necessary to study those surfaces with a STM. However, since only materials that are unreactive in ambient conditions will be studied, it was sufficient to design and assemble an air STM in order to characterize materials such us graphene, which do not have to be constrained to an UHV environment. One of the principal advantages of using an air STM rather than an UHV-STM is the significant time reduction in transferring and preparing a sample for imaging. While it can take up to two or three days to prepare a sample for imaging in UHV, a sample can be prepared for imaging in ambient conditions in just a few minutes. Also, an air STM is relatively cheap and involves a simple design, which ameliorates maintenance procedures. Due to the proximity between the tip and the sample (~ 5A), main considerations in the design for this air STM were the vibration and noise isolation of the entire system, the coarse and fine approach of the tip probe to the sample, and the electrical wiring connections. Electronic equipment from RHK Technology was used to control the STM. A detailed view of the design-assembly will be explained in the next section of this article. 2. Experimental Design Coarse and Fine Approach Design An air STM with an axially symmetric structure was designed and built in our laboratory. The use of a commercially available micromanipulator (from Vacuum Generators Limited, Hastings, England) was used to perform the vertical coarse approach of the STM head, as well as the horizontal coarse translation along the x and у axes (see Fig. 1). After the coarse approach of the STM head, the head becomes decoupled from the head holder (see Fig. 2). This helps to avoid vibrational noise transmission to the STM tip. In order to perform the fine adjustment of the tip position, a set of three ceramic piezoelectric tubes (Staveley Sensors, Inc., EBL#2 with Ni electrodes) were used to displace the decoupled STM tip, via a ramp mechanism at an approximate rate of 800nm/s to 3 µm/s, see Figs. 2(a) and (b). The dimensions of the piezoelectric tubes are as follows: 0.125" outer diameter x 0.5" length x 0.020" wall thickness. Appropriate voltages applied to the electrodes cause expansion or contraction of the tube (z motion) or bending in two orthogonal directions (A and В motion). This phenomenon is known as the reverse piezoelectric effect. The outside of the piezo tube is separated into five quadrants. The first one attaches to the nickel-plated aluminum body, which is connected to facilitate the grounding connection for all the piezo tube-legs. The other quadrants are used to move the piezo tube-legs, providing either rotation down or displacement across the ramp.  Figure 1. Schematic of electrical connections at the STM head, (bottom view) showing piezo quadrants. L labels the piezo legs and T corresponds to the tip probe. X and Y correspond to connections controlling tip displacement in the plane of the sample surface. A and В correspond to connections controlling rotation of the STM head up and down the ramp. In order to ensure the samples are properly elevated within the range of tip approach, which is dictated by the ramp for the piezoelectric legs, a set of Ni foils (~ 1 mm each) were used because it is conducting and an available material in our lab. The principal reason for using these foils is because they are sufficiently thin to allow fairly precise control of the sample's height by stacking them together. Each of the Ni foils was attached to one another using graphite tape to avoid displacement between foils. To fix the sample's position, a set of clamps was used, which also promoted better electrical connection between the sample and the ramp's base (see Fig. 3).  Figure 2. Photograph of the air STM. A) Complete view of the STM-frame and micromanipulator. The total height is 26 in. b) Closer view of the STM piezo-ramp assembly.  Figure 3. Top-view photograph of the assembly including the ramp, sample, and clamps. The sample shown is HOPG. Tip Probe A stable, conducting material that can be formed into a sharp point (ideally 1 atom) is needed for the tip. The most common materials for tip probes are tungsten and Pt/Ir. Commercially available Pt/Ir tips (Nanoprobe™ SPM Tips from Digital Instruments, model PT-ECM) with a total length of 14 mm, were used for this air STM. Pt provides better resistance to oxidation in ambient conditions than tungsten and small amounts of Ir increase the hardness of the tip. The scanning approach mechanism used for this tip was a ceramic piezoelectric material, controlled to have x and у displacements (see Figure 1 and 2b). The tip and the specimen were cleaned only with acetone followed by isopropanol and distilled water. The exposed tip was about 1.5 mm in length. It is ideal to have the exposed tip length as small as possible to avoid vibrational noise. Electrical Connections and Electronic Design Electrical connections for the STM head to the piezo tubes and the voltage bias were made with 0.003 in. and 0.010 in. diameter Kapton-coated copper wire, respectively (California Fine Wire, Co.). All wire-wire and wire-pin connections were made using solder and flux (Weller® EC2002M). The electronics used for the computer data input and output was a control module, model V-SCAN 100, and a control panel, model STM 100 from RHK Technology. These electronics are important for surface imaging in one of two ways: 1) in constant height mode, in which the tunneling current is monitored as the tip is scanned parallel to the surface and 2) in constant current mode, in which the tunneling current is maintained constant as the tip is scanned across the surface. In practice, it is most common to image the surface in constant current mode. This is achieved by adjusting the tip's height above the surface so that the tunneling current does not vary with the lateral tip position. For example, in this mode the tip will move slightly upwards as it passes over a surface atom, and conversely, slightly in towards the surface as it passes over a hollow site. This is the major concern of the feedback loop circuit, which is the most critical electronic circuit in the STM design, and is shown in Figure 4.  Figure 4. Feedback loop test diagram, which allows monitoring the stability of the STM-100 Vibration Isolation and Noise Control This section will focus on the main design considerations for the vibration isolation, which includes several methods in order to damp high and low frequency vibrations. Some common sources of noise are: 1) building vibrations due to people walking around at 1 Hz 2) building vibrations due to ventilation, and appliances at 10 to 100 Hz and 3) lowest internal resonance of typical STMs at 1 to 10 kHz. The basic idea is to make the internal resonance frequencies of the STM very high, and to mount it on a support with a very low resonance frequency. The support will follow only the low-frequency building vibrations and suppress most of the high-frequency components. The remaining low-frequency vibrations, in turn, will not disturb the STM, because they do not introduce any internal motions to the STM (it just moves as a whole structure). In order to damp the frequencies of external vibrations, the present isolation design was accomplished by a stack of stainless steel plates, separated by O-rings, as was used in the first "pocket" STM. Since the elastic material is quite; stiff, the resonance frequencies of the individual stages are quite high. However, the stack of multiple damping stages (each with different resonance frequency, since the supported mass decreases from bottom to top) is quite efficient. The wires for electrical connections as mentioned in the previous section are as thin as possible to reduce noise transmission in the STM. In addition, cardboard was placed around the STM frame to shield it from air currents. To minimize vibration interference, the system was mounted on an air cylinder vibration reducer (Newport, Stabilizer™, 1-2000 Series), which is part of an air-floating floor in order to minimize and damp noise frequencies. The next section of this article shows some results, which reflect the performance of this isolation system. 3. Results The following section presents the results for an analysis of the vibration reduction provided by the air cylinders and air-floor, and it will show some preliminary images, which indicate successful assembly of the STM and significant reduction of noise. The following vibration analysis of the air STM system was performed using the STM electronic software noise power spectrum acquisition (STM 100 from RHK Technology). Figure 5 a) and b) show the vibration spectra near the air STM with and without the vibration reduction cylinder and floating floor.  Figure 5. Noise power spectrum for air-SMT : a) without air cylinders and floating floor. b) with air cylinders and floating floor The above plots demonstrate the expected vibration noise reduction attributed to the air cylinders with the floating floor. Figure 5 a) shows a high intensity at ~ 60 Hz, which is a typical value for appliances and acoustic noises (the maximum intensity at 60Hz is approximately 90 pA/√Hz). Figure 5 b) shows the damped spectrum in the mechanical frequency region (~60Hz) using the air cylinders and the floating floor. Initial testing of the STM's functionality was performed by scanning a Au(111) surface with a 2° offset. The main purpose of using this Au sample was because it is inert, electrically conducting, and has a high step density. Steps are relatively easy surface defects to image. Some of the results of these scans are shown in Fig. 6. The images indicate the successfully designed and assembled electronics, fine approach mechanism, and piezoelectric leg functionality for the air STM. It is important to mention that the tip used for this measurement was an old tip, which may be damaged due to physical contact on surfaces. A new tip was introduced for future measurements; improved images are expected because it should have a sharper tip. The sample in Figure 6 appears to have some impurities on the surfaces due to previous experimental work.  Figure 6. STM image of Au (111) 20 offset surface The arrows in Fig. 6 a) show the step topography, typical of Au surfaces. Figure 6 b) was a zoom in scan of part of the region shown in Fig. 6 a). In order to accurately determine the resolution obtained with the air-STM, more images need to be acquired.  Figure 7. STM image of HOPG surface. The above figure (Fig. 7) shows the surface structure for the HOPG sample scanned with the air-STM. The surface appears to have a step structure, but more images need to be taken. Future work will include scanning to image the hexagonal structure of HOPG in order to calibrate the scale and optimize the resolution for the air-STM. 4. Conclusions and Outlook The vibration reduction system shows a reduction in the system vibration, having the expected behavior. The STM was tested by imaging Au(111) 2° offset surface. The air-STM was assembled with success, and minor adjustments to the tip have been made. Present and future work consists of calibrating the air STM using HOPG. Future work will also focus on the tunneling characteristics of charge effects in the air STM. Several investigations have shown the great influence of ambient humidity, giving rise to significant surface conductivity even on insulators. The successful design and assembly of this air STM design will provide a tool to characterize atomically thin films such as graphene. Аннотация Рассматривается сканирующий туннельный микроскоп на воздушной подушке для исследования тонких пленок на атомарном уровне в автоматическом режиме в условиях окружающей среды в сравнении с микроскопом с вакуумной системой. Приводится описание конструкции микроскопа для гашения вибраций, электронной части с обратной связью и способа подвода датчика к объекту контроля. Описывается эксперимент контроля пленки Au (111). Реферат Рассматривают туннельный микроскоп для сканирования двухмерных материалов на атомарном уровне. Основное преимущество использования микроскопа с воздушной подушкой над микроскопом с вакуумной системой является существенное снижение времени передачи и подготовки образца для сканирования. Микроскоп с воздушной подушкой дешевле, прост в использовании и обслуживании. Элементы конструкции, воздушная подушка и решения при проектировании микроскопа позволяют гасить высокие и низкие частоты вибраций. Вибрационный анализ системы с помощью ПО показывает эффективность использования воздушного цилиндра для снижения вибрации и воздушной подушки. Малый размер датчика устраняет возможность вибрационного шума. В вертикальной и горизонтальной плоскости датчик перемещается микроманипулятором. Конструкция из трех керамических пьезоэлектрических трубок отвечает за точный подвод датчика к объекту контроля. Поверхность сканируют в режиме постоянного тока путем настройки зазора между датчиком и поверхностью контроля. Туннельный ток устраняют боковым перемещением датчика. Обратная связь в схеме микроскопа отвечает за стабильность сканирования. Испытания работы систем микроскопа на золотой пленке Au (111) со смещением 20 подтвердили преимущества конструкции, электронной части и механизма подвода датчика. Микроскоп применяют для контроля тонких пленок на атомарном уровне в автоматическом режиме. |
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