| Ternary sulfides (A-Cu-S) with different structures can be formed when alkali metal ions are incorporated into the Cu-S lattice system, which may have different coordination numbers and different positions of copper atoms depending on the content of copper ions. They may have different optical and electrical properties and may have new applications in fields such as electronics and photoelectronics. KCu7S4 is an important one of the K-Cu-S ternary system. Its quasi-one-dimensional structure is of great significance in the study of transport phenomena in low-dimensional solids. However, it is difficult to obtain good quality crystals due to the existent of stacking fault in these copper-deficient phases. Therefore, only a few researches on K-Cu-S quasi 1D micro/nanostructures have been reported. Herein, we researched the controllable synthesis of the KCu7S4 nanobelts with good crystallinity. The electrical performances were systematical characterized. The main results are as follow:1. KCu7S4 nanobelts with widths of 200-600 nm and lengths up to several hundred micrometer have been synthesized using a solution-based method, which were characterized to be body-centered tetragonal structures with high purity and good crystallinity. The bandgap were estimated to be 1.65 eV by UV-vis absorption spectroscopy. Therefore, the strong near-infrared (NIR) absorption reveals the potential for the application in the field of NIR photodetectors.2. The resistivity of KCu7S4 nanostructures can be calculated to be about ～0.5 mΩ·cm from the electrical characterization, which reduced as the increase of the temperature, revealing the semiconductor property of the sample. Electrical transport properties of the bottom-gate field-effect transistor (FET) base on a single KCu7S4 nanobelt revealed its p-type conduction with a high hole mobility of about 870 cm2 V-1 s-1. This may be attributed to the quasi-1D conduction path along the c axis in the structure of KCu7S4.3. A KCu7S4/Cu Schottky junction was fabricated which displayed well-defined current rectifying characteristics. Obvious current hysteresis occured when the voltage sweep from -0.4 Vâ†'0 Vâ†'0.8 V and back to -0.4 V. Further measurement shows that it has a resistive switching memory characteristic with a set voltage of about 0.6 V, a current ON/OFF ratio of about 104, and a retention time>104 s. Such a memory behavior can be ascribed to the interfacial layer in which the oxygen vacancies in the unintentionally formed oxide film were believed to serve as efficient trapping centers for electrons. As-synthesized KCu7S4 nanobelts may have the potential applications in the high-performance and low-consumption nonvolatile memory devices. |
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