Reducing the thermal budget of epitaxial thin film growth has been one of the biggest challenges for the electronics industry. In this report, the room-temperature epitaxial growth of titanium nitride (TiN) thin films (∼75 nm) on (0001) Al 2 O 3 substrates is demonstrated using a pulsed laser deposition technique. In TiN thin films, the epitaxial relationship is established by X-ray diffraction for (111) TiN //(0001) Al 2 O 3 and <11̅ 0> TiN // < 101̅ 0> Al 2 O 3 which corresponds to a 30°rotation of titanium and nitrogen atoms with respect to the hexagon arrangement of aluminum atoms. An increase in the defect concentration is shown in the room-temperature thin film growth as compared to the ones grown at elevated temperature. A shift and broadening of the diffraction peaks is observed in the thin films as compared to the bulk value, indicating a higher residual tensile strain with decreasing growth temperature and an increase in defect concentration at room temperature. The increased defect concentration observed at lower growth temperature is explained by the lower energy budget that limits defect recombination and film relaxation. The residual strain in all films is dominated by the lattice mismatch (∼8.46% misfit) and defects, and not due to the thermal expansion mismatch, as Al 2 O 3 and TiN have similar coefficients of thermal expansion. Raman spectroscopy measurements also confirm an increased concentration of vacancies in TiN films grown at lower temperature. Using atomic resolution scanning transmission electron microscopy, it is shown that the room-temperature grown films contain a lower density of periodic dislocations at the film/substrate interface, a characteristic of the large misfit systems, but have more dislocations trapped within the film. The lower density of dislocations near the film−substrate interface signifies incomplete relaxation at lower temperatures. In view of more defects in the film, resistivity of the film grown at room temperature is ∼55 μΩ•cm as compared to ∼22 μΩ•cm for films grown at 650 °C, showing a similar performance at a reduced thermal budget.
Conventional microchip fabrication is energy and resource intensive. Thus, the discovery of new manufacturing approaches that reduce these expenditures would be highly beneficial to the semiconductor industry. In comparison, living systems construct complex nanometer-scale structures with high yields and low energy utilization. Combining the capabilities of living systems with synthetic DNA-/protein-based self-assembly may offer intriguing potential for revolutionizing the synthesis of complex sub-10 nm information processing architectures. The successful discovery of new biologically based paradigms would not only help extend the current semiconductor technology roadmap, but also offer additional potential growth areas in biology, medicine, agriculture and sustainability for the semiconductor industry. This article summarizes discussions surrounding key emerging technologies explored at the Workshop on Biological Pathways for Electronic Nanofabrication and Materials that was held on 16–17 November 2016 at the IBM Almaden Research Center in San Jose, CA.
Epitaxial thin film heterostructures are critical for integrating multi-functionality on a chip and creating smart structures for next-generation solid-state devices. Here, we discuss the traditional lattice matching epitaxy (LME) for small lattice misfit and domain matching epitaxy (DME), which handles epitaxial growth across the misfit scale, where lattice misfit strain is predominant and can be relaxed completely, meaning that only the thermal and defect strains remain upon cooling. In low misfit systems, all three sources contribute to the residual strain upon cooling, as result of incomplete lattice relaxation. In the second part of the chapter, we will discuss the two critical contributors to the stress of the epitaxial film: the thermal coefficient of expansion mismatch and the lattice plane misfit. In the last part of the chapter, we will focus on unique cases where room temperature epitaxial growth is possible in nitride and oxide thin films.
The multiferroic properties of mixed valence perovskites such as lanthanum strontium manganese oxide (LaSrMnO) (LSMO) demonstrate a unique dependence on oxygen concentration, thickness, strain, and orientation. To better understand the role of each variable, a systematic study has been performed. In this study, epitaxial growth of LSMO (110) thin films with thicknesses ∼15 nm are reported on epitaxial magnesium oxide (111) buffered AlO (0001) substrates. Four LSMO films with changing oxygen concentration have been investigated. The oxygen content in the films was controlled by varying the oxygen partial pressure from 1 × 10 to 1 × 10 Torr during deposition and subsequent cooldown. X-ray diffraction established the out-of-plane and in-plane plane matching to be (111) ∥ (0001) and ⟨11̅0⟩ ∥ ⟨101̅0⟩ for the buffer layer with the substrate, and an out-of-plane lattice matching of (110) ∥ (111) for the LSMO layer. For the case of the LSMO growth on MgO, a novel growth mode has been demonstrated, showing that three in-plane matching variants are present: (i) ⟨11̅0⟩ ∥ ⟨11̅0⟩, (ii) ⟨11̅0⟩ ∥ ⟨101̅⟩, and (iii) ⟨11̅0⟩ ∥ ⟨01̅1⟩. The atomic resolution scanning transmission electron microscopy (STEM) images were taken of the interfaces that showed a thin, ∼2 monolayer intermixed phase while high-angle annular dark field (HAADF) cross-section images revealed 4/5 plane matching between the film and the buffer and similar domain sizes between different samples. Magnetic properties were measured for all films and the gradual decrease in saturation magnetization is reported with decreasing oxygen partial pressure during growth. A systematic increase in the interplanar spacing was observed by X-ray diffraction of the films with lower oxygen concentration, indicating the decrease in the lattice constant in the plane due to the point defects. Samples demonstrated an insulating behavior for samples grown under low oxygen partial pressure and semiconducting behavior for the highest oxygen partial pressures. Magnetotransport measurements showed ∼36.2% decrease in electrical resistivity with an applied magnetic field of 10 T at 50 K and ∼1.3% at room temperature for the highly oxygenated sample.
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