Applications of Hard X-ray Photoelectron Spectroscopy

Applications of Hard X-ray Photoelectron Spectroscopy Applications of Hard X-ray Photoelectron Spectroscopy to bulk materials Jingru Chi ABSTRACT X-ray Photoelectron Spectroscopy is a powerful, relevant and non-destructive method for studying atoms, molecules and surfaces [1]. However, investigations are limited to atoms, molecules and surfaces since low energy electrons limit the depth resolution, resulting in three-dimensional bulk state cannot be detected. Hard X-ray Photoelectron Spectroscopy (HAXPES) with high kinetic energy photoelectrons uses excitation by X-ray of 2-15keV and a high energy analyzer which make it possible to measure bulk and determine bulk electronic structure properties of materials [2]. The recoil effects of photoelectrons in valence band states and core levels are the principal studies of HAXPES. In this paper, HAXPES uses undulator synchrotron X-rays at SPring-8. The results of high energy photoelectron spectroscopy of the valence bands and sensitivity of bulk have shown that the measured valence band spectra are indispensable in studying the bulk electronic structure. Introduction The Nobel Prize in 1981 was awarded to Kai Siegbahn for developing the method of Electron Spectroscopy for Chemical Analysis (ESCA), now which is presented as X-ray Photoelectron Spectroscopy (XPS). Since then, XPS becomes one of the most useful and non-destructive techniques for analyzing the electronic structure of atoms, molecules and surfaces. In early studies, XPS uses Mo KÃŽ ± (= 17.479keV), Cr KÃŽ ± (= 5.417keV) or Cu KÃŽ ± (= 8.047 keV) hard X-ray sources. Gradually it out of date with the discovery that lower energy soft X-rays such as the Mg KÃŽ ± (= 1253.6eV) and Al KÃŽ ± (= 1486.7eV) sources has the higher energy resolution [3]. Reducing incident energy improved the surface sensitivity of XPS. However, soft X-rays source limits the depth resolution to 5nm for Angle-Resolved X-ray Photoelectron Spectroscopy (ARXPS) and 10nm for inelastic loss analysis [4], so it cannot detect the deeply buried layers without destructive ways like ion sputtering and etching which are time-c onsuming and hard to control. In the last few years, the developments of new bright synchrotron photon sources, the availability of monochromators with a resolving power about 105, and electron analyzers which can analyze the 10 keV electrons with meV resolution have created the new possibilities for Hard X-ray Photoelectron Spectroscopy (HAXPES) [5], which made it possible to analyze the bulk structure without using destructive methods. HAXPES has not been well-developed until the appearance of the third generation synchrotrons, which can generate high-brilliance, high-flux X-rays that enables one to perform experiments with the HAXPES in very low photoionization cross-section [1]. As well the developments of electron analyzer with the high kinetic energy range also contributed to improve HAXPES measurements [6]. The superiority of HAXPES is the considerable probing depth owing to the increased electron mean free path [7], made it possible to detect the electronic structure of bulk materials. With the excitation energy of 8 keV, the escape energy can be greater than 90 Ã… [1]. With high kinetic energies of electrons, the coral level and the valence band can be detected in the bulk materials. According to these advantages, HAXPES is one of the best ways to perform sensitive photoemission spectroscopy on correlated systems such as thin films, multilayer systems and devices [1]. Several investigations on bulk materi als have been reported. One is the measurement of the valence band of Co2Mn1−xFexSi (x = 0, 0.5, 1) be excited by photons which have energy about 8 keV [8, 9]. This experiment was the proof that the XPS with hard X-rays has better sensitivity on bulk electronic structure than the conventional XPS with soft X-rays. Fundamentals of HAXPES Model of photoionization using hard X-rays When use the conventional theoretical model to describe the photoemission, including the differential cross-section of photoionization for photon energies from 2 keV to 15 keV, the model based on the power series expansion of the electron-photon interaction operator cannot perfectly explain photoemission though just using a limited number of the terms of the expansion [2]. However, a more complex expansion of the electron-photon interaction operator developed by Fujikawa [11, 12] contained all the electric dipole operators and other multipole terms can explain it well. These models indicate that contributions from electric quadrupole and magnetic dipole transitions cannot be ignored anymore when photoelectrons are excited by high energy X-rays and beyond the electric dipole transitions [2]. Systems Fig. 1. HEARP Lab system [10] There are just so many kinds of HAXPES, here just introduce the HEARP Lab system. In this system, it needs the monochromatic X-ray source with 5–6 keV photon energies and the high energy electron analyzer with angular resolution capability for the measurements of takeoff angle dependence and X-ray photoelectron diffraction [10]. To meet these requirements, HEARP uses the Cr KÃŽ ± X-ray source, a wide acceptance objective lens, and a high energy version of VG SCIENTA R4000 analyzer [10], as it showed in Fig. 1. A Cr KÃŽ ± X-ray source is shown in Fig. 2(a). The main body contains the water cooling system and Cr target. At the first, the monochromatic Cr KÃŽ ± X-rays are emitted by a focused electron beam with the maximum acceleration energy of 20keV, then X-rays go through the bent crystal monochromator with a 300mm Rowland circle and focus onto a sample surface [10], as schematically shown in Fig. 2(b). The X-ray spot size ranges from 1.5ÃŽ ¼m to 200ÃŽ ¼m by raster scanning of the electron beam [10]. (b) (a) Fig. 2. X-ray source [10]. (a) Photograph of UHV compatible flange mounted Cr KÃŽ ± X-ray source [10]. (b) Schematic diagram of X-ray source. The electron beam is focused on a water cooled Cr target [10] and it excite Cr KÃŽ ± X-rays. Then it monochromatized by an elliptically bent Ge crystal with 422 reflection [10] and direct irradiated to the sample surface. The objective lens, as it shown in Fig. 3(a), is set in front of the analyzer. The angle acceptance of the lens is about  ±7 °, when it is combined with the VG SCIENTA R4000 10 KV hemispherical analyzer, the angle acceptance can achieve to  ±35 ° [10]. The magnification factor is 5, as well the magnification factor of analyzer input lens is 5, so the total magnification factor is 25 [10], and the working distance is 11mm from the aperture [10]. (a) Fig. 3 Performance The performance of HEARP system is evaluated by measuring Au 3d5/2 photoelectrons emitted from an Au strip. The total energy resolution is 0.53 eV [13]. The result of the experiment showed the acceptance angle is  ±35 ° and a resolution less than 0.5 ° [10]. When it is provided with the objective lens, the acquisition time for the Au 3d spectrum excited by the same Cr KÃŽ ± source is 16 min, which is seven times better than without the objective lens [10]. Table 1 shows the differences in HEARP Lab system and HXPES at BL47XU beamline system. Table 1 Comparison of HEARP Lab system with HXPES at BL47XU beamline system. They all have the same analyzer with the same pass energy of 200 eV. In the Lab system, it uses entrance slit of curved 0.8mm, beamline system uses curved 0.8mm. The X-ray excitation power is 45W (15 kW, 3.0 mA) [10]. Applications References [1] Siham Ouardi, Gerhard H. Fecher, Claudia Felser, ‘Bulk electronic structure studied by hard X-ray photoelectron spectroscopy of the valence band: The case of intermetallic compounds,’ Journal of Electron Spectroscopy and Related Phenomena, 190 (2013) 249–267. [2] Là ¡szlà ³ Kà ¶và ©r, ‘X-ray photoelectron spectroscopy using hard X-rays,’ Journal of Electron Spectroscopy and Related Phenomena, 178–179 (2010) 241–257. [3] M. Taguchi, Y.Takata, A.Chainani, ‘Hard X-ray photoelectron spectroscopy: A few recent applications,’ Journal of Electron Spectroscopy and Related Phenomena 190 (2013) 242–248. [4] P. Risterucci, O. Renault, E. Martinez, B. Detlefs, V. Delaye, J. Zegenhagen, C. Gaumer, G. Grenet, and S. Tougaard, ‘Probing deeper by hard x-ray photoelectron spectroscopy,’ Applied Physics Letters 104 (2014) 051608. [5] Ronny Knut, Rebecka Lindblad, Mihaela Gorgoi, Hà ¥kan Rensmo, Olof Karis, ‘High energy photoelectron spectroscopy in basic and applied science: Bulk and interface electronic structure’, Journal of Electron Spectroscopy and Related Phenomena 190 (2013) 278–288. [6] S. Ueda, ‘Application of hard X-ray photoelectron spectroscopy to electronic structure measurements for various functional materials,’ Journal of Electron Spectroscopy and Related Phenomena, 190 (2013) 235–241. [7] C. Dallera, L. Duo, L. Braicovich, G. Panaccione, G. Paolicelli, B. Cowie, J. Zegen- hagen, ‘Results and perspectives in hard X-ray photoemission spectroscopy (HAXPES) from solids’, Appl. Phys. Lett. 85 (2004) 4532. [8] B. Balke, G.H. Fecher, H.C. Kandpal, C. Felser, K. Kobayashi, E. Ikenaga, J.-J. Kim, S. Ueda, ‘Properties of the quaternary half-metal-type Heusler alloy Co2Mn1−xFexSi,’ Phys. Rev. B 74 (2006) 104405. [9] G.H. Fecher, B. Balke, S. Ouardi, C. Felser, G. Schà ¶nhense, E. Ikenaga, J.J. Kim, S. Ueda, K. Kobayashi J., ‘High energy, high resolution photoelectron spectroscopy of Co2Mn1−xFexSi,’ Phys. D: Appl. Phys. 40 (2007) 1576. [10] Keisuke Kobayashi, Masaaki Kobata, Hideo Iwai, ‘Development of a laboratory system hard X-ray photoelectron spectroscopy and its applications,’ Journal of Electron Spectroscopy and Related Phenomena, 190 (2013) 210–221. [11] Takashi Fujikawa, Rie Suzuki,Hiroko Arai, Hiroshi Shinotsuka,Là ¡szlà ³ Kà ¶và ©r, ‘Nondipole effects in photoemission angular distribution excited by high-energy X-rays’, J. Electron Spectrosc. Relat. Phenom. 159 (2007) 14. [12] Rie Suzuki,Hiroko Arai,Hiroshi Shinotsuka,Takashi Fujikawa, ‘Theory of High-Energy Photoemission’, e-J. Surf. Sci. Nanotechnol. 3 (2005) 373. [13] Kobata M,Pà ­s I,Iwai H,Yamazui H,Takahashi H,Suzuki M,Matsuda H,Daimon H,Kobayashi K., ‘Development of the hard-X-ray angle resolved X-ray photoemission spectrometer for laboratory use’, Anal Sci.26 (2010) 227-32. [12] . In Heusler thin films of Co2MnSi and Fig. 1 shows the thin films covered with MgO, SiOx and the protective layers with AlOx or Ru, the thickness of the MgO and SiOx layers are from 1 nm to 20 nm. When it is covered with AlOx layer,

Julius Caesar Essay -- essays research papers fc

Julius Caesar’s legacy and attributes are just as robust today as they were in his time. From the time he took power to the time of his death he accomplished more than many other men would have done in a lifetime. He brought the Roman Empire to its height and from his death on, the Empire did nothing but fall. He was one of the world’s greatest leaders and probably the best. At the age of 15 Caesar became head of his family when his father died in 85bc. His family wanted him to pursue a religious career as the priest of Jupiter but Caesar had other plans. He wanted to dive head long into a political career. He took maters into his own hands when in 84bc he married Cornelia the daughter of one of Rome’s stronger leaders at the time, Cornelius Cinna (Schlesinger 30). Cinna took power in 82bc when Rome’s leader at the time Gaius Marius died. Marius was married to Caesar’s Aunt Julia. Marius was killed in battle with one of his great enemies Sulla. Soon after this battle Sulla died also, but he still had many allies. Marius had let Caesar help him while he was leader by doing small jobs. Caesar gained much experience while helping out Marius. When Caesar was 25 he set sail for the island of Rhodes. But, on the way a band of pirates captured the ship and kidnapped him. While his family was raising ransom money he was a very difficult guest for the pirates. He strolled boldly around their ship and pointed out weaknesses in their sword fighting technique and told them he would kill them all after he was released. They were entertained by this young man but did not believe the threat (Green 19). His family finally paid his ransom. Soon after it was paid, Caesar learned that the government was not going to take action and pursue the pirates. Caesar took matters into his own hands. He organized a fleet of ships, captured the pirates and crucified their whole gang. The news of this spread quickly, and Caesar was both admired and criticized for acting so quickly. By age 30, Caesar was making Sulla’s allies very worried. But 30 was not too young for a roman so full of ambition. In 69bc, Caesar was serving as governor in farther Spain, administering Roman laws to Spanish tribes and subduing those who resisted. He went to go see the statue of Alexander the Great in the city of Cadiz. Alexander was a leader who had conquered much of the world by the age of 30. Caes... ... he died, it is amazing to think of all that he accomplished in his life. Also it is amazing to think of all that he could have accomplished if he had lived. His legacy lived on through Octavius, who named himself emperor of Rome and like all roman emperors that followed he took the name of Caesar. If he had stayed alive the Roman Empire could have conquered all of the Eastern Hemisphere. Rome defiantly benefited from him. Rome was the most powerful nation at the time and would have stayed that way for much longer if Julius Caesar had not been murdered. Works Cited Green, Robert. Julius Caesar. New York. Franklin watts publishing company, 1996 May, Robin. Julius Caesar and the Romans. East Sussex. Wayland publishing, 1984 Schlesinger, Arthur M. Caesar. Boston. Chelsea house publishers, 1987 Suetonius. The lives of the 12 Caesar's. Willamstown, MA. Corner house publishers, 1987 Blooming, Mike H. â€Å"Hero or Villain† 6 April, 1995

Feminism In The Handmaids Tale Essay -- Feminism Feminist Women Criti

Feminism In The Handmaid's Tale      Ã‚  Ã‚   Feminism as we know it began in the mid 1960's as the Women's Liberation Movement. Among its chief tenants is the idea of women's empowerment, the idea that women are capable of doing and should be allowed to do anything men can do. Feminists believe that neither sex is naturally superior. They stand behind the idea that women are inherently just as strong and intelligent as the so-called stronger sex. Many writers have taken up the cause of feminism in their work. One of the most well known writers to deal with feminist themes is Margaret Atwood. Her work is clearly influenced by the movement and many literary critics, as well as Atwood herself, have identified her as a feminist writer. However, one of Atwood's most successful books, The Handmaid's Tale, stands in stark contrast to the ideas of feminism. In fact, the female characters in the novel are portrayed in such a way that they directly conflict with the idea of women's empowerment.    On the surface, The Handmaid's Tale appears to be feminist in nature. The point-of-view character and narrator is a woman and thus we see the world through a woman's eyes. There's much more to the story than that, though. Atwood doesn't show us our world. She shows us a newly created world in which women lack the freedoms that they currently take for granted. This dystopian society is completely controlled by men. Of course, the men have help from the Aunts, a crack team of brainwashers that run the reeducation centers and teach the handmaids how to be slaves. These characters really don't speak well for womankind for two reasons. First of all, it's difficult to tell who their real life counterpart is, assuming that this... ...st writers. It's obvious that Atwood intentionally set herself apart from these writers with The Handmaid's Tale. At times, she seems to disagree with them completely, such as when she shows pornography in a favorable manner. At other times, she portrays feminists themselves as the powerful women they would like to be seen as, but it's always with full disclosure of their human frailty. Atwood never bashes feminism. Instead, she shows both sides of it. Like everything else in the novel, feminism is shown to have good and bad elements. Even in Atwood's brave new world, there is no black and white.    Sources Atwood, Margaret. The Handmaid's Tale. New York: Fawcett Crest, 1985. Moore, Pamela, Atwood, Margaret: The Handmaid's Tale. Boston, MS: Houghton Mifflin, 1986. Internet www.wsu.edu:8000/~brains/science_fiction/handmaid.html   

The Year of the Woman Essay -- mh

The Year of the Woman Reporters portray female and male candidates differently when covering campaigns for political office. In order to counteract the biased coverage in the papers the women of the 1992 Senate race used 30-second advertising spots to assert their key issue stances and strengths. Though this was not the sole purpose of their ads, they were very much geared toward compensating for the lack of fair coverage they were receiving in the news. Ultimately they persevered. Through verbal and nonverbal content, as defined by Lynda Lee Kaid, women designed their ads to portray a high level of competence. 1992 is widely known as 'The Year of the Woman,' when 5 women won Senate seats and 24 new women were elected to the House. "All male Senate races received more press coverage than races which included female candidates,' but despite male biased journalistic media coverage, 'women of the 1992 election succeeded with strong campaign spots," that helped them redefine themselves to the public and win c onstituent votes. Though women and men receive an equal amount of coverage by newspapers, "the content of the coverage that women receive as opposed to men, during an election is extremely different and male biased." Newspaper readers are more likely to read about a female candidate's personal life, appearance, or personality while reading about a male's stance on governmental issues. This gives the man more credibility as a candidate. Compared to coverage of male candidates, coverage of a female candidate is, "more personal, less issue based, and less likely to include evidence or reasoning to support quoted remarks". Ultimately women are portrayed as less informed on issues and instead as icons rather than educated citize... ...er women in this study won representation of their state. Each woman focused her ad on something different. It is clear that Braun's ad is heavily laden with endorsements, legislative achievements and highlights of power and leadership while at the same time concentrating a huge portion of the ad on family values. Boxer's theme was to fight for change and Dianne Fienstein highlighted her achievements in the face of undue hardship. Seargant and Ferraro took their ads and focused on highlighting power and leadership. Ultimately all of the women had feminine ad campaigns that were positive outlooks on women rather than weak, negative and superficially concerned. Though men started out with an unfair advantage of positive journalistic media coverage in 1992, women created ad campaigns that overcame the unbalance and won more seats in the House and Senate than ever before.

The Mass-marketing of Working Class Culture :: Exploratory Essays Research Papers

The Mass-marketing of Working Class Culture The fads of the father are visited on the son: we've all seen how adult fads are given down to children. We've seen how cargo pants have trickled down, thanks to the Gap, Baby Gap, and Old Navy (all corporations owned by The Limited, Inc.). Cargo pants have always been a mystery to me. The attractive thing about them is storage (which I'll get to later), blandness and personal appearance. I only considered wearing cargo pants because they'd hide how chunky my thighs are. And they're beige and boring--they thus go with anything. I also don't understand this fascination with looking working-class (In a recent copy of Vogue, there were ritzy, high-priced versions of lumberjack clothing). There's absolutely nothing wrong with that and I don't want to sound like an elitist, because I'm by no means not working-class. I just wonder why this a trend, why white collar workers want to look like they work with their hands. But this fascination with storage, with having so many products presents a problem. Cargo pants were designed so workers could essentially wear their toolbox. Today's kids wearing cargo pants don't need that space for hammers and nails. To avoid acknowledging that cargo pants are a silly trend, wearers unconsciously seek to fill their pockets. As Lacan might say, empty pockets remind us of our lacks. Cargo pants only encourage the reckless. The Gap, like any other capitalist corporation, wants consumers to spend oodles of money. Providing more storage space in a pair of pants allows for children and teens to spend even more money filling them. What the Gap has done is transformed the meaning of cargo pants. It is a redefinition: today's cargo pants wearers aren't laborers, they're spenders. Isn't that a glorious thing, the Gap may ask us. It's a way of showing how the upper class has always stepped all over the lower class, taking what aspects of its culture it likes and discarding the individuals involved. We've seen this over and over, but it usually has been a race's culture that has been used while the individuals are considered meaningless by the ruling classes. This is happening again today with Latin culture. White culture takes what few things it likes (namely Jennifer Lopez and Ricky Martin, maybe a salsa beat, and some Tex-Mex food), and celebrates it as all Latin culture has to offer, ignoring debates about the "Latinness" of such aspects anyway.

Animal Cruelty and Youth Violence Essay -- Animals Kids Pet Pets Child

There are over seventy million cats and fifty-five million dogs in the United States, yet the number of reported cases of neglect, or abuse is severely lacking (Davidson 1). Animal abuse is an ongoing dilemma in this country; recent studies have indicated child animal cruelty offenders often go on to pursue disturbing acts of criminal behavior. This nation simply does not have standardized legislation across the nation as a preventative method of dealing with this predicament. Many states treat animal abuse too leniently, and this is bad because youthful offenders often times will go on to perform criminal acts later in life, therefore anti-youth violence organizations and animal abuse prevention organizations need to join forces in order to enhance existing laws and to better educate America’s youth. It was not until recently people were first beginning to discover that animals do indeed have rights. Brief History: It was not until 1966 that the nation finally realized these kind creatures could in fact feel pain and neglect, when the Animal Welfare Act was finally passed. According to Congress’s Public Law 89-544 Act of August 24, 1966, the use of animals in lab tests, the transportation, sale, and handling of dogs, cats and certain other animals is now regulated by the Secretary of Agriculture (1). Sample State Animal Cruelty Laws: Nevada: Recently it has become mandatory for Nevada juvenile court systems to obtain some form of psychological treatment for animal cruelty offenders (â€Å"States Look at Stricter Laws† 1). This is great news for the state of Nevada; unfortunately this mandatory regulation does not exist in all states. Idaho and Illinois: According to Howard Davidson, director of the ABA center ... ...t Stricter Animal Cruelty Laws." State Legislatures 27.4 (2001): 8pp. 1 Mar. 2006 . "Pawprint Navigation Bar Image." Retrieved from Google.com on April 1, 2006. . "State Animal Anti-Cruelty Law Provisions." The Humane Society of the United States. 2005. 28 Feb. 2006. . "The Link between Animal Cruelty and Child Maltreatment." APA Center on Children and the Law (June 1998). 25 Feb. 2006 . United States Congress. 89th Congress, H.R. 13881 An Act. Public Law 89-544 11 of August 24, 1996. June 1998. 20 Feb. 2006 . "University at Albany Image." Retrieved from Google.com on April 25, 2006. .

Causes of Plagiarism Essay -- Plagiarism Essays

Plagiarism has become a major issue among university students around the world. Academic misconduct has been a concern to those teaching at the universities. Hence, to prevent this from occurring the educational bodies have implemented measures to avoid plagiarism. Presently, the newly recruited students are informed of the consequences of plagiarism and that stern action is in place (Ashworth, Bannister, & Thorne,1997,p.1). However, plagiarism can be divided into two parts: deliberate and inadvertent. Presented here are the reasons why student plagiarism is considered quite high at western universities, even though many of the university students do not mean to cheat. There are three reasons as follows: (1) lack of clear understanding about the concept; (2) lack of knowledge about citation and referencing skills; and (3) poor time management. The first focus is on definitions of plagiarism and the differences between two types of plagiarism, reasons for inadvertent plagiarism, and l astly why international students have became the most plagiarising students in western universities. Plagiarism is one type of academic misconduct which is treated seriously in today’s universities. Plagiarism is defined as † literary theft, stealing ( by copying ) the words or ideas of someone else and passing them off as one’s own without crediting the source†(Handa & Power, n.d., p.66). For example, use of any material which is taken from any sources, such as books, electric journals, the Internet, or from other people’s work comprises plagiarism. There are two types of plagiarism: (1) deliberate (intention to cheat); (2) inadvertent (no intention to cheat). If students do it on purpose or intend to cheat, it means that the students have cheated... ...), 471-488. http://www.elearning.tcu.edu/resources/faculty/turnitin/Why%20Students%20Plagiarize.pdf Peter Ashwortha, Philip Bannistera, Pauline Thornea, "Guilty in whose eyes? University students' perceptions of cheating and plagiarism in academic work and assessment" Studies in Higher Education, Volume 22, Issue 2, 1997 Roig, Miguel (1997) "Can Undergraduate Students Determine Whether Text Has Been Plagiarized," The Psychological Record: Vol. 47: Iss. 1, Article 7. Available at: http://opensiuc.lib.siu.edu/tpr/vol47/iss1/7 Walker, John. "Student Plagiarism in Universities: What are we Doing About it?" Higher Education Research & Development, Volume 17, Issue 1, 1998 http://www.tandfonline.com/doi/abs/10.1080/0729436980170105?journalCode=cher20 Wang, Y. (2008). University student online plagiarism. International Journal on E-Learning, 7(4), 743-757.