Abstract
Resistive RAM is a promising, relatively new type of memory with fast switching characteristics. Metal chalcogenide films have been used as the amorphous semiconductor layer in these types of devices. The amount of crystallinity present in the films may be important for both reliable operation and increased longevity of the devices. Germanium sulfide films can be used for these devices, and a possible way to tune the crystalline content of the films is by substituting Sn for some of the Ge atoms in the film. Thin films of GexSnySz containing varying amounts of tin were deposited in a plasma enhanced chemical vapor deposition reactor. Films with 2%, 8%, 15%, 26%, and 34% atomic percentage Sn were deposited to determine crystallinity and structural information with XRD and Raman spectroscopy. Based on these depositions it was determined that at about 8% Sn content and below, the films were largely amorphous, and at about 26% Sn and above, they appeared to be largely crystalline. At 15% Sn composition, which is between 8% and 26%, the film is more a mixture of the two phases. Based on this information, current-voltage (IV) curves of simple memory switching devices were constructed at 5% Sn (in the amorphous region), at 25% Sn (in the crystalline region), and at 15% (in the mixed region). Based on the IV curves from these devices, the 15% composition gave the best overall switching behavior suggesting that a certain degree of order in the semiconductor layer is important for RRAM devices.
Highlights
Studies have shown that the incorporation of Sn or Sb into the germanium chalcogenide layer increases their stability of these semiconductor layers for use in these devices [4] [5]
Previous studies by our group have shown that PECVD is an efficient method for depositing both germanium sulfide and germanium selenide thin films with good thickness and quality control [6] [7], and slight modification of this methodology would likely provide an efficient method for production of germanium chalcogenide films with controlled percentages of Sn incorporation
The ability to control the percentage of Sn deposited into the germanium chalcogenide thin film layer provides an opportunity to study tin’s effect on the material properties of the germanium chalcogenide thin films, and allows for a deeper understanding of how Sn incorporation may lead to improved phase memory and resistive-RAM (RRAM) memory
Summary
Studies have shown that the incorporation of Sn or Sb into the germanium chalcogenide layer increases their stability of these semiconductor layers for use in these devices [4] [5]. Previous studies by our group have shown that PECVD is an efficient method for depositing both germanium sulfide and germanium selenide thin films with good thickness and quality control [6] [7], and slight modification of this methodology would likely provide an efficient method for production of germanium chalcogenide films with controlled percentages of Sn incorporation. The ability to control the percentage of Sn deposited into the germanium chalcogenide thin film layer provides an opportunity to study tin’s effect on the material properties of the germanium chalcogenide thin films, and allows for a deeper understanding of how Sn incorporation may lead to improved phase memory and resistive-RAM (RRAM) memory. The 4+ ions of each have diameters of 45 and 53 pm respectively
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