Microscopy, 2014, Vol. 63, No. S1
i11
Fig. 1. (a) Topographic image of a KCl(100) surface obtained in [Py1,4]FAP, (b) 2D Δf map obtained on an Au(111)/[Py1,4]FAP interface.
doi: 10.1093/jmicro/dfu050 Spin-selective Imaging by Magnetic Exchange Force Microscopy Using Ferromagnetic Resonance Yasuhiro Sugawara, Eiji Arima, Yoshitaka Naitoh and Yan Jun Li Department of Applied Physics, Graduate School of Engineering, Osaka University Techniques to analyze the surface of magnetic memory devices with high spatial resolution are very important to develop today’s information technology. The magnetic exchange force is an interaction between spins and is very important for analyzing magnetic properties. Magnetic exchange force microscopy (MExFM), which can detect the magnetic exchange force between the magnetic tip and the magnetic surface, has achieved the atomic-resolution imaging of the spin state on anti-ferromagnetic surface of NiO(001) [1]. In MExFM, however, the separation between a structure and a magnetic state on the surface has not been performed. Here, we propose a new MExFM using ferromagnetic resonance to separate the magnetic and non-magnetic tip-sample interaction. In this method, magnetic tip apex is irradiated by the frequencymodulated microwave with the frequency of ferromagnetic resonance.
Fig. 1. (a) Structure of NiO(001) surface and (b) its image ( phase) obtained with MExFM using ferromagnetic resonance. (4 nm x 4 nm).
The magnetization of magnetic tip apex is modulated from on resonance to off resonance. Tip-sample interaction is measured with frequency modulation method. Magnetic images are obtained by detecting the modulation component of the frequency shift of the oscillating cantilever using a lock-in amplifier. Topographic images are obtained by the feedback signal for the constant tip-sample interaction. As a magnetic tip, magnetic cantilever tip coated with FePt with a high coercivity was used to detect the magnetic exchange force without an external magnetic field [2]. We performed imaging on antiferromagnetic material NiO(001) surface (Fig. 1(a)) by MExFM using ferromagnetic resonance. We obtained spin selective image in atomic resolution (Fig. 1(b)). This is the first demonstration of magnetization modulation of the magnetic tip apex using ferromagnetic resonance as well as the separation of the magnetic and non-magnetic tip-sample interaction in MExFM.
References 1. Kaiser U., et al., Nature 446, 522 (2007). 2. Peilmeier F., et al., Phys. Rev. Lett., 110, 266101 (2013). doi: 10.1093/jmicro/dfu053
Microscopic techniques bridging between nanoscale and microscale with an atomically sharpened tip - field ion microscopy/scanning probe microscopy/ scanning electron microscopy Masahiko Tomitori and Akira Sasahara School of Materials Science, Japan Advanced Institute of Science and Technology
E-mail: [email protected] Over a hundred years an atomistic point of view has been indispensable to explore fascinating properties of various materials and to develop novel functional materials. High-resolution microscopies, rapidly developed during the period, have taken central roles in promoting materials science and related techniques to observe and analyze the materials. As microscopies with the capability of atom-imaging, field ion microscopy (FIM), scanning tunneling microscopy (STM), atomic force microscopy (AFM) and transmission electron microscopy (TEM) can be cited, which have been highly evaluated as methods to ultimately bring forward the viewpoint of reductionism in materials science. On one hand, there have been difficulties to derive useful and practical information on large (micro) scale unique properties of materials using these excellent microscopies and to directly advance the engineering for practical materials. To make bridges over the gap between an atomic scale and an industrial engineering scale, we have to develop emergence science step-by-step as a discipline having hierarchical structures for future prospects by
Downloaded from http://jmicro.oxfordjournals.org/ at Ryerson University on April 26, 2015
achieved. We also developed electrochemical FM-AFM and investigated metal/IL interfaces. Figure 1(b) shows a 2D Δf map obtained on an Au(111)/[Py1,4]FAP interface. The electrode potential was shifted from −0.4 V vs. Pt-quasi-ref. (hereafter called “V”) to −1.6 V during the imaging. The multiple solvation layers on the interface was imaged, and we found that the solvation structure was shifted by approximately 0.5 nm to the Au(111) surface when the potential was shifted. This result indicates that reconstruction of the ions on the interface was directly visualized.
Microscopy, 2014, Vol. 63, No. S1
i12
References 1. Sasahara A., Pang C. L., Tomitori M. J. Phys. Chem. C 114 (2010) 20189. 2. Le T. T. U., Sasahara A., Tomitori M. J. Phys. Chem. C 117 (2013) 23621. doi: 10.1093/jmicro/dfu040
SPM characterization of next generation solar cells under light irradiation: Optoelectronic study from nano to macroscopic scale Nobuyuki Ishida and Daisuke Fujita National Instutite for Materials Science, 1-2-1 Sengen, Tsukuba, 305-0047, Japan
E-mail: [email protected] Solar cells (SCs) that contain elaborate nanostructures, such as quantum dots and quantum wells, have been rigorously investigated as a way to harvest a wide range of the solar spectrum [1]. However, the energy conversion efficiency of those SCs still remains low. For the further improvement of the device performance, a much deeper understanding of the role of nanostructures in the photovoltaic conversion process is essential to gain the effective design criteria. To achieve this, local electronic properties including electrical potential, energy states, and charge distribution around the excitation centers have to be characterized under light irradiation since they govern the behavior of excited carriers. These properties have so far been indirectly deduced from macroscopic characterization such as current-voltage (I-V) measurement; however, it is not sufficient to clarify rather complicated roles of the nanostructures [2]. Thus, a direct measurement of those properties with high spatial resolution is required to understand the detailed mechanisms of the photovoltaic conversion process. To this end, we have been developing a platform for performing scanning tunneling microscopy/spectroscopy (STM/ STS), atomic force microscopy (AFM), and Kelvin probe force microscopy (KPFM) working under light irradiation conditions. Here, we outline the characterization of a multiple quantum well (QW) SC based on III-V compounds that is expected to be a potential candidate of intermediate band type SC. First, we show the electrical potential measurements along the p-i-n junction of the SC using KPFM in air. Measurements were performed in open and short circuit configurations under light irradiation conditions [Fig.1]. We demonstrate that the dependence of the open circuit voltage on the intensity of light can be successfully measured by careful interpretation of the KPFM data. Second, we introduce some examples of the atomic scale characterization of the multiple QW using ultrahigh vacuum STM including the atomic arrangement, electronic states, and band profile. Also, charge accumulation at the QW is discussed based on the topographic measurement under light irradiation. References 1. Tanabe K., Energies 2, 504 (2009). 2. Ding Y., et al., Jpn. J. Appl. Phys. 51, 10ND08 (2012). doi: 10.1093/jmicro/dfu042
Fig. 1. (a) Schematic illustration of measurement system of KPFM in air. (b) Effect of light irradiation on potential profile in open circuit configuration.
Downloaded from http://jmicro.oxfordjournals.org/ at Ryerson University on April 26, 2015
combining nanoscale and microscale techniques; as promising ways, the combined microscopic instruments covering the scale gap and the extremely sophisticated methods for sample preparation seem to be required. In addition, it is noted that spectroscopic and theoretical methods should implement the emergence science. Fundamentally, the function of microscope is to determine the spatial positions of a finite piece of material, that is, ultimately individual atoms, at an extremely high resolution with a high stability. To define and control the atomic positions, the STM and AFM as scanning probe microscopy (SPM) have successfully demonstrated their power; the technological heart of SPM lies in an atomically sharpened tip, which can be observed by FIM and TEM. For emergence science we would like to set sail using the tip as a base. Meanwhile, it is significant to extend a model sample prepared for the microscopies towards a microscale sample while keeping the intrinsic properties found by the microscopies. In this study we present our trial of developing microscopic combined instruments among FIM, field emission microscopy (FEM), STM, AFM and scanning electron microscopy (SEM), in which we prepared and characterized the tips for the SPM, and in addition, the sample preparation to take a correlation between nanoscale and microscale properties of functional materials. Recently, we developed a simple sample preparation method of a rutile single crystal TiO2 covered with an epitaxially-grown monolayer of SiO2 by annealing the crystals in a furnace at high temperatures in air; the crystal samples were placed into a quartz container in the furnace [1]. The vapor of SiO evaporated from the quartz container were adsorbed on the crystal while the crystal surfaces being fully oxidized in air. The SiO2-TiO2 composite systems are promising to protect catalytic TiO2 performance; the photo-catalytic activity is kept by coating with hard and stable SiO2 layers and to extend the lifetime of water super-hydrophilicity even in dark, though understanding of their properties is insufficient due to the lack of techniques to fabricate a well-characterized system on a nanoscale to conduct control experiments. The SiO2 overlayers were observed by low energy electron diffraction (LEED) in vacuum and frequencymodulation (FM) AFM in water [1,2], and water contact angles (WCA) were measured [2]. Although the WCA measurement seems a classic characterization, this method possesses a high potential to make a bridge by controlling the environmental conditions. We will discuss the details.
i11
Fig. 1. (a) Topographic image of a KCl(100) surface obtained in [Py1,4]FAP, (b) 2D Δf map obtained on an Au(111)/[Py1,4]FAP interface.
doi: 10.1093/jmicro/dfu050 Spin-selective Imaging by Magnetic Exchange Force Microscopy Using Ferromagnetic Resonance Yasuhiro Sugawara, Eiji Arima, Yoshitaka Naitoh and Yan Jun Li Department of Applied Physics, Graduate School of Engineering, Osaka University Techniques to analyze the surface of magnetic memory devices with high spatial resolution are very important to develop today’s information technology. The magnetic exchange force is an interaction between spins and is very important for analyzing magnetic properties. Magnetic exchange force microscopy (MExFM), which can detect the magnetic exchange force between the magnetic tip and the magnetic surface, has achieved the atomic-resolution imaging of the spin state on anti-ferromagnetic surface of NiO(001) [1]. In MExFM, however, the separation between a structure and a magnetic state on the surface has not been performed. Here, we propose a new MExFM using ferromagnetic resonance to separate the magnetic and non-magnetic tip-sample interaction. In this method, magnetic tip apex is irradiated by the frequencymodulated microwave with the frequency of ferromagnetic resonance.
Fig. 1. (a) Structure of NiO(001) surface and (b) its image ( phase) obtained with MExFM using ferromagnetic resonance. (4 nm x 4 nm).
The magnetization of magnetic tip apex is modulated from on resonance to off resonance. Tip-sample interaction is measured with frequency modulation method. Magnetic images are obtained by detecting the modulation component of the frequency shift of the oscillating cantilever using a lock-in amplifier. Topographic images are obtained by the feedback signal for the constant tip-sample interaction. As a magnetic tip, magnetic cantilever tip coated with FePt with a high coercivity was used to detect the magnetic exchange force without an external magnetic field [2]. We performed imaging on antiferromagnetic material NiO(001) surface (Fig. 1(a)) by MExFM using ferromagnetic resonance. We obtained spin selective image in atomic resolution (Fig. 1(b)). This is the first demonstration of magnetization modulation of the magnetic tip apex using ferromagnetic resonance as well as the separation of the magnetic and non-magnetic tip-sample interaction in MExFM.
References 1. Kaiser U., et al., Nature 446, 522 (2007). 2. Peilmeier F., et al., Phys. Rev. Lett., 110, 266101 (2013). doi: 10.1093/jmicro/dfu053
Microscopic techniques bridging between nanoscale and microscale with an atomically sharpened tip - field ion microscopy/scanning probe microscopy/ scanning electron microscopy Masahiko Tomitori and Akira Sasahara School of Materials Science, Japan Advanced Institute of Science and Technology
E-mail: [email protected] Over a hundred years an atomistic point of view has been indispensable to explore fascinating properties of various materials and to develop novel functional materials. High-resolution microscopies, rapidly developed during the period, have taken central roles in promoting materials science and related techniques to observe and analyze the materials. As microscopies with the capability of atom-imaging, field ion microscopy (FIM), scanning tunneling microscopy (STM), atomic force microscopy (AFM) and transmission electron microscopy (TEM) can be cited, which have been highly evaluated as methods to ultimately bring forward the viewpoint of reductionism in materials science. On one hand, there have been difficulties to derive useful and practical information on large (micro) scale unique properties of materials using these excellent microscopies and to directly advance the engineering for practical materials. To make bridges over the gap between an atomic scale and an industrial engineering scale, we have to develop emergence science step-by-step as a discipline having hierarchical structures for future prospects by
Downloaded from http://jmicro.oxfordjournals.org/ at Ryerson University on April 26, 2015
achieved. We also developed electrochemical FM-AFM and investigated metal/IL interfaces. Figure 1(b) shows a 2D Δf map obtained on an Au(111)/[Py1,4]FAP interface. The electrode potential was shifted from −0.4 V vs. Pt-quasi-ref. (hereafter called “V”) to −1.6 V during the imaging. The multiple solvation layers on the interface was imaged, and we found that the solvation structure was shifted by approximately 0.5 nm to the Au(111) surface when the potential was shifted. This result indicates that reconstruction of the ions on the interface was directly visualized.
Microscopy, 2014, Vol. 63, No. S1
i12
References 1. Sasahara A., Pang C. L., Tomitori M. J. Phys. Chem. C 114 (2010) 20189. 2. Le T. T. U., Sasahara A., Tomitori M. J. Phys. Chem. C 117 (2013) 23621. doi: 10.1093/jmicro/dfu040
SPM characterization of next generation solar cells under light irradiation: Optoelectronic study from nano to macroscopic scale Nobuyuki Ishida and Daisuke Fujita National Instutite for Materials Science, 1-2-1 Sengen, Tsukuba, 305-0047, Japan
E-mail: [email protected] Solar cells (SCs) that contain elaborate nanostructures, such as quantum dots and quantum wells, have been rigorously investigated as a way to harvest a wide range of the solar spectrum [1]. However, the energy conversion efficiency of those SCs still remains low. For the further improvement of the device performance, a much deeper understanding of the role of nanostructures in the photovoltaic conversion process is essential to gain the effective design criteria. To achieve this, local electronic properties including electrical potential, energy states, and charge distribution around the excitation centers have to be characterized under light irradiation since they govern the behavior of excited carriers. These properties have so far been indirectly deduced from macroscopic characterization such as current-voltage (I-V) measurement; however, it is not sufficient to clarify rather complicated roles of the nanostructures [2]. Thus, a direct measurement of those properties with high spatial resolution is required to understand the detailed mechanisms of the photovoltaic conversion process. To this end, we have been developing a platform for performing scanning tunneling microscopy/spectroscopy (STM/ STS), atomic force microscopy (AFM), and Kelvin probe force microscopy (KPFM) working under light irradiation conditions. Here, we outline the characterization of a multiple quantum well (QW) SC based on III-V compounds that is expected to be a potential candidate of intermediate band type SC. First, we show the electrical potential measurements along the p-i-n junction of the SC using KPFM in air. Measurements were performed in open and short circuit configurations under light irradiation conditions [Fig.1]. We demonstrate that the dependence of the open circuit voltage on the intensity of light can be successfully measured by careful interpretation of the KPFM data. Second, we introduce some examples of the atomic scale characterization of the multiple QW using ultrahigh vacuum STM including the atomic arrangement, electronic states, and band profile. Also, charge accumulation at the QW is discussed based on the topographic measurement under light irradiation. References 1. Tanabe K., Energies 2, 504 (2009). 2. Ding Y., et al., Jpn. J. Appl. Phys. 51, 10ND08 (2012). doi: 10.1093/jmicro/dfu042
Fig. 1. (a) Schematic illustration of measurement system of KPFM in air. (b) Effect of light irradiation on potential profile in open circuit configuration.
Downloaded from http://jmicro.oxfordjournals.org/ at Ryerson University on April 26, 2015
combining nanoscale and microscale techniques; as promising ways, the combined microscopic instruments covering the scale gap and the extremely sophisticated methods for sample preparation seem to be required. In addition, it is noted that spectroscopic and theoretical methods should implement the emergence science. Fundamentally, the function of microscope is to determine the spatial positions of a finite piece of material, that is, ultimately individual atoms, at an extremely high resolution with a high stability. To define and control the atomic positions, the STM and AFM as scanning probe microscopy (SPM) have successfully demonstrated their power; the technological heart of SPM lies in an atomically sharpened tip, which can be observed by FIM and TEM. For emergence science we would like to set sail using the tip as a base. Meanwhile, it is significant to extend a model sample prepared for the microscopies towards a microscale sample while keeping the intrinsic properties found by the microscopies. In this study we present our trial of developing microscopic combined instruments among FIM, field emission microscopy (FEM), STM, AFM and scanning electron microscopy (SEM), in which we prepared and characterized the tips for the SPM, and in addition, the sample preparation to take a correlation between nanoscale and microscale properties of functional materials. Recently, we developed a simple sample preparation method of a rutile single crystal TiO2 covered with an epitaxially-grown monolayer of SiO2 by annealing the crystals in a furnace at high temperatures in air; the crystal samples were placed into a quartz container in the furnace [1]. The vapor of SiO evaporated from the quartz container were adsorbed on the crystal while the crystal surfaces being fully oxidized in air. The SiO2-TiO2 composite systems are promising to protect catalytic TiO2 performance; the photo-catalytic activity is kept by coating with hard and stable SiO2 layers and to extend the lifetime of water super-hydrophilicity even in dark, though understanding of their properties is insufficient due to the lack of techniques to fabricate a well-characterized system on a nanoscale to conduct control experiments. The SiO2 overlayers were observed by low energy electron diffraction (LEED) in vacuum and frequencymodulation (FM) AFM in water [1,2], and water contact angles (WCA) were measured [2]. Although the WCA measurement seems a classic characterization, this method possesses a high potential to make a bridge by controlling the environmental conditions. We will discuss the details.
