{"id":40,"date":"2017-08-30T08:17:50","date_gmt":"2017-08-30T15:17:50","guid":{"rendered":"http:\/\/chem.wsu.edu\/hipps\/?page_id=40"},"modified":"2026-05-01T12:10:58","modified_gmt":"2026-05-01T19:10:58","slug":"chemical-selectivity-in-scanning-tunneling-microscopy","status":"publish","type":"page","link":"https:\/\/chem.wsu.edu\/hipps\/chemical-selectivity-in-scanning-tunneling-microscopy\/","title":{"rendered":"Chemical Selectivity in Scanning Tunneling Microscopy"},"content":{"rendered":"<div class=\"wsu-hero wsu-width--full wsu-pattern--wsu-light-radial-left \">\n\t\n\t<div class=\"wsu-image-frame wsu-image-frame--fill\">\n\t<img decoding=\"async\" src=\"https:\/\/wpcdn.web.wsu.edu\/wp-chem\/uploads\/sites\/1718\/2017\/08\/UHV-STM-9-2017-2.jpg\"\n\t\tsrcset=\"https:\/\/wpcdn.web.wsu.edu\/wp-chem\/uploads\/sites\/1718\/2017\/08\/UHV-STM-9-2017-2.jpg 1632w, https:\/\/wpcdn.web.wsu.edu\/wp-chem\/uploads\/sites\/1718\/2017\/08\/UHV-STM-9-2017-2.jpg 396w, https:\/\/wpcdn.web.wsu.edu\/wp-chem\/uploads\/sites\/1718\/2017\/08\/UHV-STM-9-2017-2.jpg 768w, https:\/\/wpcdn.web.wsu.edu\/wp-chem\/uploads\/sites\/1718\/2017\/08\/UHV-STM-9-2017-2.jpg 792w, https:\/\/wpcdn.web.wsu.edu\/wp-chem\/uploads\/sites\/1718\/2017\/08\/UHV-STM-9-2017-2.jpg 990w, https:\/\/wpcdn.web.wsu.edu\/wp-chem\/uploads\/sites\/1718\/2017\/08\/UHV-STM-9-2017-2.jpg 1188w\"\n\t\tsizes=\"(max-width: 1632px) 100vw, 1632px\"\n\t\talt=\"Microscopy equipment in lab\"\n\t\tstyle=\"object-position: 50% 50%\"\n\t\t\/>\n<\/div>\n\n\t<div class=\"wsu-overlay wsu-pattern-after wsu-overlay--dark-left wsu-pattern--none\"><\/div>\n\t<div class=\"wsu-hero__content\">\n\t\t<div class=\"wsu-hero__caption\">\n\t\t\t\t\t\t\t\t\t<h1 id=\"title-id-6a09887e023b0\" class=\"wsu-title wsu-hero__title\"><span>Chemical Selectivity in Scanning Tunneling Microscopy<\/span><\/h1>\n\t\t\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t<\/div>\n<\/div>\n\n\n<div class=\"wsu-row crimson-back wsu-row--single\" >\r\n    \n<div class=\"wsu-column\"  style=\"\">\r\n\t\n\n<h2 class=\"wp-block-heading\">Data Acquired with a McAllister UHV-STM and Nanoscope III Electronics.<\/h2>\n\n\n\n<p>Courtesy of Professor K.W. Hipps, Department of Chemistry, Washington State University.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<p>While the acquisition of sub-molecular structure by STM has been a reality for almost 10 years, the instances where one could clearly determine the chemical nature of a surface species have been few and problematic. In the series of images presented here, one can clearly identify cobalt(II) phthalocyanine [CoPc] from copper(II) phthalocyanine [CuPc]. While these two species are almost identical from a crystallographic perspective, they differ in one very dramatic way &#8211; their d-orbital occupations. Cobalt(II) is a d<sup>7&nbsp;<\/sup>system having a half filled d<sub>z<\/sub><span style=\"font-size: xx-small;\">2&nbsp;<\/span>orbital. This orbital can be used to carry charge across the plane of the molecule, and the energy required to fill it is similar to the Fermi energy of the sample. Copper(II), on the other hand, is a d<sup>9<\/sup> system, and addition of an electron to the d<sub>x2-y2 <\/sub>orbital requires several eV more energy than the Fermi energy. The effects of this can be seen in the actual STM data taken from a monolayer of CoPc adsorbed on Au(111) [shown below]. Also shown in the figure are the images of three space-filling models of CoPc. Note the very high central regions associated with the partially filled d<sub>z<\/sub>2 orbital.<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter\"><img decoding=\"async\" loading=\"lazy\" width=\"776\" height=\"572\" src=\"https:\/\/s3.wp.wsu.edu\/uploads\/sites\/1718\/2017\/08\/copc132s.gif\" alt=\"The effects of the addition of an electron to the dx2-y2 orbital requires several eV more energy than the Fermi energy. The effects of this can be seen in the actual STM data taken from a monolayer of CoPc adsorbed on Au(111) [shown below]. Also shown in the figure are the images of three space-filling models of CoPc. Note the very high central regions associated with the partially filled dz2 orbital.\" class=\"wp-image-44\"\/><figcaption class=\"wp-element-caption\">The effects of the addition of an electron to the dx2-y2 orbital requires several eV more energy than the Fermi energy. The effects of this can be seen in the actual STM data taken from a monolayer of CoPc adsorbed on Au(111) [shown here]. Also shown in the figure are the images of three space-filling models of CoPc. Note the very high central regions associated with the partially filled dz2 orbital.<\/figcaption><\/figure><\/div>\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<p>When a monolayer of CuPc on Au(111) is imaged by STM (as shown below), the d orbitals are unable to participate in the tunneling current and the Cu(II) ion appears as a hole in the center of each 4-leaf clover shaped molecule. Since the ionic diameters of Co(II) and Cu(II) differ by less than 0.02 nm, the height differences are clearly due to the details of d orbital occupation. (See: <i>J. Phys. Chem.<\/i>, June 1996: K.W. Hipps, Xing Lu, X.D. Wang, and Ursula Mazur).<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter\"><img decoding=\"async\" loading=\"lazy\" width=\"597\" height=\"450\" src=\"https:\/\/s3.wp.wsu.edu\/uploads\/sites\/1718\/2017\/08\/cupc119s-1.gif\" alt=\"When a monolayer of CuPc on Au(111) is imaged by STM (as shown here), the d orbitals are unable to participate in the tunneling current and the Cu(II) ion appears as a hole in the center of each 4-leaf clover shaped molecule. Since the ionic diameters of Co(II) and Cu(II) differ by less than 0.02 nm, the height differences are clearly due to the details of d orbital occupation. (See: J. Phys. Chem., June 1996: K.W. Hipps, Xing Lu, X.D. Wang, and Ursula Mazur).\" class=\"wp-image-46\"\/><figcaption class=\"wp-element-caption\">When a monolayer of CuPc on Au(111) is imaged by STM (as shown here), the d orbitals are unable to participate in the tunneling current and the Cu(II) ion appears as a hole in the center of each 4-leaf clover shaped molecule. Since the ionic diameters of Co(II) and Cu(II) differ by less than 0.02 nm, the height differences are clearly due to the details of d orbital occupation. (See: <i>J. Phys. Chem.<\/i>, June 1996: K.W. Hipps, Xing Lu, X.D. Wang, and Ursula Mazur).<\/figcaption><\/figure><\/div>\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<p>This difference in d-orbital occupation can be used to clearly identify individual molecules adsorbed on surfaces. This is demonstrated in the Figure below wherein a mixed composition layer of CoPc and CuPc was formed on Au(111). It is immediately obvious which are the CoPc (bright centers) and which are the CuPc (dark centers). Moreover, this image difference can be used to monitor surface properties such as diffusion and multi-layer formation (See: <i>J.Amer. Chem. Soc.<\/i> 1996: K.W. Hipps, Xing Lu, X.D. Wang, and Ursula Mazur).<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter\"><img decoding=\"async\" loading=\"lazy\" width=\"604\" height=\"450\" src=\"https:\/\/s3.wp.wsu.edu\/uploads\/sites\/1718\/2017\/08\/cocu063s.jpg\" alt=\"This difference in d-orbital occupation can be used to clearly identify individual molecules adsorbed on surfaces. This is demonstrated in this Figure wherein a mixed composition layer of CoPc and CuPc was formed on Au(111). It is immediately obvious which are the CoPc (bright centers) and which are the CuPc (dark centers). Moreover, this image difference can be used to monitor surface properties such as diffusion and multi-layer formation (See: J.Amer. Chem. Soc. 1996: K.W. Hipps, Xing Lu, X.D. Wang, and Ursula Mazur).\" class=\"wp-image-47\" srcset=\"https:\/\/wpcdn.web.wsu.edu\/wp-chem\/uploads\/sites\/1718\/2017\/08\/cocu063s.jpg 604w, https:\/\/wpcdn.web.wsu.edu\/wp-chem\/uploads\/sites\/1718\/2017\/08\/cocu063s-396x295.jpg 396w\" sizes=\"(max-width: 604px) 100vw, 604px\" \/><figcaption class=\"wp-element-caption\">This difference in d-orbital occupation can be used to clearly identify individual molecules adsorbed on surfaces. This is demonstrated in the Figure below wherein a mixed composition layer of CoPc and CuPc was formed on Au(111). It is immediately obvious which are the CoPc (bright centers) and which are the CuPc (dark centers). Moreover, this image difference can be used to monitor surface properties such as diffusion and multi-layer formation (See: <i>J.Amer. Chem. Soc.<\/i> 1996: K.W. Hipps, Xing Lu, X.D. Wang, and Ursula Mazur).<\/figcaption><\/figure><\/div>\n<\/div>\r\n\n<\/div>","protected":false},"excerpt":{"rendered":"","protected":false},"author":1308,"featured_media":182,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"_wsuwp_accessibility_report":null},"categories":[],"tags":[],"wsuwp_university_location":[],"wsuwp_university_org":[],"_links":{"self":[{"href":"https:\/\/chem.wsu.edu\/hipps\/wp-json\/wp\/v2\/pages\/40"}],"collection":[{"href":"https:\/\/chem.wsu.edu\/hipps\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/chem.wsu.edu\/hipps\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/chem.wsu.edu\/hipps\/wp-json\/wp\/v2\/users\/1308"}],"replies":[{"embeddable":true,"href":"https:\/\/chem.wsu.edu\/hipps\/wp-json\/wp\/v2\/comments?post=40"}],"version-history":[{"count":10,"href":"https:\/\/chem.wsu.edu\/hipps\/wp-json\/wp\/v2\/pages\/40\/revisions"}],"predecessor-version":[{"id":407,"href":"https:\/\/chem.wsu.edu\/hipps\/wp-json\/wp\/v2\/pages\/40\/revisions\/407"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/chem.wsu.edu\/hipps\/wp-json\/wp\/v2\/media\/182"}],"wp:attachment":[{"href":"https:\/\/chem.wsu.edu\/hipps\/wp-json\/wp\/v2\/media?parent=40"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/chem.wsu.edu\/hipps\/wp-json\/wp\/v2\/categories?post=40"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/chem.wsu.edu\/hipps\/wp-json\/wp\/v2\/tags?post=40"},{"taxonomy":"wsuwp_university_location","embeddable":true,"href":"https:\/\/chem.wsu.edu\/hipps\/wp-json\/wp\/v2\/wsuwp_university_location?post=40"},{"taxonomy":"wsuwp_university_org","embeddable":true,"href":"https:\/\/chem.wsu.edu\/hipps\/wp-json\/wp\/v2\/wsuwp_university_org?post=40"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}