1. Composition-matched molecular “solders” for semiconductors
by Dmitriy S. Dolzhnikov, Hao Zhang, Jaeyoung Jang, Jae Sung Son, Matthew G. Panthani, Tomohiro Shibata, Soma Chattopadhyay, and Dmitri V. Talapin
Science
Volume 347(6220):
January 23, 2015
Copyright © 2015, American Association for the Advancement of Science

2. Fig. 1 Structure and properties of CdTe22– compounds.
Structure and properties of CdTe22– compounds. (A) Crystal structure of K2CdTe2·2N2H4 determined by using single crystal x-ray diffraction. Hydrogen atoms are not shown for clarity. (B) Solubility of Na2CdTe2 in different solvents can be tuned by cation exchange from sodium (Na+) to tetratethylammonium (NEt4+) or didodecyldimethylammonium (DDA+). Polymeric [CdTe22−]∞ ions can be cross-linked with Cd2+ ions, forming stable “CdTe-gel.” [CdTe22−]∞ ions can serve as ligands for luminescent CdTe quantum dots (QDs). (C) Depending on solvent polarity and coordinating ability, [CdTe22−]∞ can exist in two equilibrium forms.
Dmitriy S. Dolzhnikov et al. Science 2015;347:
Copyright © 2015, American Association for the Advancement of Science

3. Fig. 2 Transport properties of CdSe NCs after ligand exchange.
Transport properties of CdSe NCs after ligand exchange. (A) Absorption spectra of 4.7-nm CdSe NCs capped with ODPA and [Cd2Se3]2− ligands. (Inset) Photograph of the solution of [Cd2Se3]2−-capped CdSe NCs. (B) Scheme of a FET device with 10-nm ZrO2 gate dielectric and Al source and drain electrodes. (C) Transfer characteristics and (D) output characteristics of an FET with a channel made of spin-coated 4.7 nm [Cd2Se3]2−-capped CdSe NCs annealed at 250°C for 30 min. FET channel width and length are 1500 and 30 μm, respectively. The inset in (C) shows the linear and saturation regime electron mobility extracted from FET transfer characteristics (9).
Dmitriy S. Dolzhnikov et al. Science 2015;347:
Copyright © 2015, American Association for the Advancement of Science

4. Fig. 3 Soldering various materials with novel chalcogenidometallates.
Soldering various materials with novel chalcogenidometallates. Scanning electron microscopy images of (A) ball-milled PbTe microparticles annealed at 500°C for 30 min. (B) Film of similar PbTe microparticles annealed in the presence of 5 wt % Na2PbTe2. (C) Film made of Bi2Te3 microparticles annealed in the presence of 5 wt % (N2H5)4Bi2Te5. (D) Film made of CdTe NCs annealed in the presence of 20 wt % “CdTe-gel.” The films were annealed at 500°C, 400°C, and 450°C for 30 min, respectively. (Insets) Film optical micrographs. (E) 3D blocks of PbTe, Bi2Te3, and CdTe cast by using graphite molds of various shapes from microparticles mixed with corresponding “solders”: Na2PbTe2 for PbTe, Na4Bi2Te5 for Bi2Te3, and Na2CdTe2 for CdTe. (F) A photograph showing two CdTe crystals with mechanically polished (111) faces soldered with Na2CdTe2 at 500°C.
Dmitriy S. Dolzhnikov et al. Science 2015;347:
Copyright © 2015, American Association for the Advancement of Science