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Ge 2 Sb 2 Te 5 ͑GST͒ thin films were deposited on SiO 2 /Si and TiN/Si substrates by cyclic metallorganic chemical vapor deposition using Ge͑i-C 4 H 9 ͒ 4 , Sb͑i-C 3 H 7 ͒ 3 , Te͑i-C 3 H 7 ͒ 2 as Ge, Sb, and Te precursors, respectively, with the help of Ar + H 2 plasma at temperatures ranging from 180 to 290°C. The application of plasma power was essential in obtaining a high growth rate and stoichiometric GST thin films. The chemical composition of the films was properly controlled by the cycling ratio and sequence of each precursor pulse. The stoichiometric films grown at 200°C showed a smooth surface morphology, highest density, and lowest impurity concentration. GST film was selectively grown inside the contact hole having a TiN/W plug.

GST thin films were deposited by combined ALD and CVD at a temperature of 200 °C. The selective growth behavior of GST on the contact hole was observed. This was explained by the preferential nucleation property of Sb and subsequent adsorption of Te and Ge on the Sb nuclei on SiO2.

Imaging mechanism of piezoresponse force microscopy in capacitor structures" (2008). Alexei Gruverman Publications. 23.

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The required time for voltage-pulse-induced resistive switching of 40-nm-thick TiO2 thin films integrated in a contact-type structure (Pt top and TiN bottom contact, contact area ∼0.07μm2) was studied as a function of pulse voltage. For off→on switching at least 2V was necessary and the minimum switching times were ∼20ns at 2V and ∼10ns at 3V. For on→off switching, a minimum switching time of 5μs was obtained at 2.5V. The resistance of the on-state device was also dependent on the switching voltage and time.

This study concerned the effect of the substrate on the nucleation and growth behavior of Ge 2 Sb 2 Te 5 (GST) thin films deposited by a combination of plasma-enhanced chemical vapor deposition (for Sb and Te) and plasma-enhanced atomic layer deposition (for Ge) processes at wafer temperatures ranging from 100 to 200°C using Ge(i-C 4 H 9 ) 4 , Sb(i-C 3 H 7 ) 3 , and Te(i-C 3 H 7 ) 2 as the Ge, Sb, and Te precursors, respectively. Several oxide and nitride layers that were formed on the Si substrate were concerned as substrates. The nucleation of the GST films on the SiO 2 , Si 3 N 4 , and ZrO 2 substrates was seriously retarded (long incubation cycles) compared to those on the TiN and TiO 2 substrates, where smooth film growth with negligible incubation cycles was achieved. The GST film did not grow at all on the HfO 2 substrate. The reason for the enhanced nucleation and growth properties of GST on the TiO 2 and TiN (partially oxidized) substrates was related to the formation of a GeO 2 phase and the charge exchange effect of a partially reduced Ti oxide. On the other hand, the SiO 2 surface remained insulating during deposition, which inhibited GST nucleation. The different nucleation behaviors also influenced the crystallization behavior of the film, which in turn altered the saturated film growth rates. It is believed that the crystallized GST surface reduced the activation energy for the chemisorption of the precursors, which enhanced the saturated growth rate.