University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln Faculty Publications -- Chemistry Department Published Research - Department of Chemistry 2012 CRYSTALLINE NANO STRUCTURES Barry Chin Li Cheung Joseph Reese Brewer Nirmalendu Deo Follow this and additional works at: https://digitalcommons.unl.edu/chemfacpub Part of the Analytical Chemistry Commons, Medicinal-Pharmaceutical Chemistry Commons, and the Other Chemistry Commons This Article is brought to you for free and open access by the Published Research - Department of Chemistry at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in Faculty Publications -- Chemistry Department by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. US00824707OB2 (12) United States Patent (10) Patent No.: US 8.247,070 B2 Cheung et al. (45) Date of Patent: Aug. 21, 2012 (54) CRYSTALLINENANOSTRUCTURES (51) Int. Cl. B32B 9/00 (2006.01) (76) Inventors: Barry Chin Li Cheung. Lincoln, NE (52) U.S. Cl. ........ 428/366; 428/364; 428/397: 428/399; (US); Joseph Reese Brewer, Lincoln, 428/401 NE (US);); Nirmalendu Deo, Lincoln, NE (58) Field of Classification Search .................. 428/364, 428/366,397, 399, 401 (*) Notice: Subject to any disclaimer, the term of this See application file for complete search history. patent is extended or adjusted under 35 U.S.C. 154(b) by 431 days. (56) References Cited (21) Appl. No.: 12/447,836 U.S. PATENT DOCUMENTS 3,711,908 A * 1/1973 Broers ............................ 445/50 (22) PCT Filed: Oct. 30, 2007 6,903,499 B2* 6/2005 Terui et al. ... 313,309 2005, 0133254 A1* 6/2005 Tsakalakos ................... 174,261 (86). PCT No.: PCT/US2007/083037 * cited by examiner (2),S371 (4) (c)(1), Date: Jan. 26, 2010 Primary Examiner — Andrew Piziali- 0 (74) AttOrney, Agent, or FirmF. — Advent IP,IF, P.C.,F.U., L.L.OL.L.U. (87) PCT Pub. No.: WO2008/127393 (57) ABSTRACT PCT Pub. Date: Oct. 23, 2008 The present invention comprises nano obelisks and nano (65) Prior Publication Data structures and methods and processes for same. The nano f obelisks of the present invention are advantageous structures US 2010/01 19825A1 May 13, 2010 for use as electron source emitters. For example, the ultra O O sharp obelisks can be used as an emitter source to generate Related U.S. Application Data highly coherent and high energy electrons with high current. (60) Provisional application No. 60/863.564, filed on Oct. 30, 2006. 11 Claims, 11 Drawing Sheets U.S. Patent Aug. 21, 2012 Sheet 1 of 11 US 8,247,070 B2 Fig. 1 U.S. Patent Aug. 21, 2012 Sheet 2 of 11 US 8,247,070 B2 Fig. 2 U.S. Patent Aug. 21, 2012 Sheet 3 of 11 US 8,247,070 B2 Fig. 3 U.S. Patent Aug. 21, 2012 Sheet 4 of 11 US 8,247,070 B2 Fig. 4 U.S. Patent Aug. 21, 2012 Sheet 5 of 11 US 8,247,070 B2 Fig. 5 U.S. Patent Aug. 21, 2012 Sheet 6 of 11 US 8,247,070 B2 Fig. 6 U.S. Patent Aug. 21, 2012 Sheet 7 of 11 US 8,247,070 B2 Fig. 7 U.S. Patent Aug. 21, 2012 Sheet 8 of 11 US 8,247,070 B2 S. s& 32:3:2::::::::si & 1. Fig. 8 U.S. Patent Aug. 21, 2012 Sheet 9 of 11 US 8,247,070 B2 Obelisk pyramidal top height (920 °C) 753 + 138 nm. O 500 1000 Height (nm) Fig. 9 U.S. Patent Aug. 21, 2012 Sheet 10 of 11 US 8,247,070 B2 Obelisk pyramidai top height (945 °C) 29 S2 in 4.s 3 Obelisks (94.5 °C) (9; 10.802.20 8 0 50 1000 Height (nm) 0 4, 8 12 16 20 Cone angle (8) Fig. 10 U.S. Patent Aug. 21, 2012 Sheet 11 of 11 US 8,247,070 B2 Energy (keV) Fig.11 US 8,247,070 B2 1. 2 CRYSTALLINE NANOSTRUCTURES FIG. 4 is a schematic illustration depicting a growth mechanism of the present invention. CROSS-REFERENCE TO RELATED FIG. 5 shows a tunneling electron microscope (TEM) APPLICATIONS images of a lanthanum hexaboride nano-obelisk of the present invention. This application is a U.S. National Application of Interna FIG. 6 shows a TEM images of lanthanum hexaboride tional Application PCT Application No. PCT/US2007/ nanowire of the present invention. 083037 filed on Oct. 30, 2007, which claims the benefit of FIG. 7 shows an SEM images of a time trial growth of the priority from U.S. Provisional Patent Application No. 60/863, lanthanum hexaboride nano-obelisk of the present invention. 564 filed on Oct. 30, 2006. The disclosures of International 10 FIG. 8 shows a set of SEM images an EDX scan of the Application PCT Application No. PCT/US2007/083037 and lanthanum hexaboride nano-obelisk of the present invention. FIG.9 shows a TEM image of an LaB nano-scale obelisk, U.S. Provisional Patent Application No. 60/863.564 are and a histogram of pyramidal top heights. incorporated herein by reference. FIG. 10 is a set of TEM images of an LaB nano-scale 15 obelisk, and histograms of tip angles and the heights of the FIELD OF THE INVENTION pyramidal tops for a sample. FIG. 11 is a set of scanning transmission electron micro This invention relates generally to ultra sharp nano obe Scope (STEM) images of an LaBe nano-scale obelisks and lisks, and nanostructures made of low work function materi EDX spectra at different points on the obelisk. als, and methods and processes for same. DETAILED DESCRIPTION OF THE INVENTION BACKGROUND OF THE INVENTION The present invention comprises nano obelisks, and nano Recent materials research has suggested that the Carbon structures and methods and processes for same. nanotubes are considered by some to be the most promising 25 The nano obelisks of the present invention are advanta electron emitting materials because of their Small tip radius geous structures for use as electron Source emitters. For (approx. 4 nm), which leads to a significant improvement in example, the ultra sharp obelisks can be used as an emitter turn on Voltage and current density over current devices. (See Source to generate highly coherent and high energy electrons M. S. Wang et al., J. Phys. Chem. B 2006, 110,9397-9042: N. with high current. These obelisks are useful for the fabrica Jonge et al., Nature 2002, 420, 393-395, 461; W. Zhu et al., 30 tion of highly efficient field electron emitters with various Appl. Phys. Lett. 1999, 75, 873-875) In another example, applications ranging from electron guns to field emission lanthanum hexaboride (LaB) nanowire synthesized by displays. For example, the obelisks of the present invention Zhang et al. shows current densities that are one order of can be used a electron gun construction materials for fabri magnitude larger than commercial W/ZrO tips (i.e., the cations of better electron guns which use less energy and brightest commercially available field emitting material) at 35 provide higher and more coherent current with lower extrac more favorable working conditions (e.g., room temperature tion Voltage. In this embodiment, the electron guns can be and 800 V versus 1800° C. and 3000 V). (H. Zhanget al., Adv. used as electron Source for electron microscopes. The elec Mat. 2006, 18, 87-91) tron guns can also be used as electron Source for generation of However, in view of at least the foregoing, a need exists for Soft X-rays and/or gas ionizers. The electron guns can also be the development of high aspect ratio nano-structures for use 40 used as electron source for field emission displays Such as in electron emitting materials could enhance the emission Surface-conduction Electron-emitter Display (SED). The properties of current devices while simultaneously making electron guns can be used for electronbeam lithography. The the working conditions more practical. electron guns can also be used for a very intense, local X-ray Source. Such an X-ray source could be used for killing cancer BRIEF SUMMARY OF THE INVENTION 45 tumors, or other medical procedures requiring accuracy and localization. The present invention comprises nano obelisks and nano In an embodiment of the present invention, the nano obe structures, and methods and processes for same. lisks comprise lanthanum hexaboride (LaB). Lanthanum The nano obelisks of the present invention are advanta hexaboride is among the group of materials with the lowest geous structures for use as electron Source emitters. 50 work function. Accordingly, lanthanum hexaboride needs These and other advantageous features of the present only a very Small amount of input energy to emitone electron. invention will be in part apparent and in part pointed out Also, lanthanum hexaboride is relatively inert to oxidation. In herein below. this embodiment, the materials and the crystalline form of these materials have been used as electron emitter sources BRIEF DESCRIPTION OF DRAWINGS 55 (i.e., electron guns) ranging from electron microscopes to the electron guns in cathode ray tube (CRT) displays or televi For a better understanding of the present invention, refer sions. ence may be made to the accompanying drawings in which: In another embodiment, the nano obelisks comprise the FIG. 1 is a scanning electron microscope (SEM) image of elements or mixture of elements of the lanthanide series com lanthanum hexaboride nanomaterials growth, at low precur 60 bined with hexaboride. In another embodiment, the nano Sor material flux, of the present invention. obelisks comprise neodymium iron boride. In another FIG. 2 is a SEM image of lanthanum hexaboride nanoma embodiment, the nano obelisks comprise calcium hexaboride terials growth, at medium precursor material flux, of the (CaB).