We investigate the structural and quantum transport properties of isotopically enriched 28 Si/ 28 SiO 2 stacks deposited on 300-mm Si wafers in an industrial CMOS fab. Highly uniform films are obtained with an isotopic purity greater than 99.92%. Hall-bar transistors with an oxide stack comprising 10 nm of 28 SiO 2 and 17 nm of Al 2 O 3 (equivalent oxide thickness of 17 nm) are fabricated in an academic cleanroom. A critical density for conduction of 1.75 × 10 11 cm −2 and a peak mobility of 9800 cm 2 /Vs are measured at a temperature of 1.7 K. The 28 Si/ 28 SiO 2 interface is characterized by a roughness of = 0.4 nm and a correlation length of = 3.4 nm. An upper bound for valley splitting energy of 480 μeV is estimated at an effective electric field of 9.5 MV/m. These results support the use of wafer-scale 28 Si/ 28 SiO 2 as a promising material platform to manufacture industrial spin qubits.

Thin heteroepitaxial films of Si1−x−yGexCy have been grown on (100)Si substrates using atmospheric pressure chemical vapor deposition at 625 °C. The crystallinity, composition, and microstructure of the SiGeC films were characterized using Rutherford backscattering spectrometry, secondary-ion-mass spectrometry, and cross-sectional transmission electron microscopy. The crystallinity of the films was very sensitive to the flow rate of C2H4 which served as the C source. Films with up to 2% C were epitaxial with good crystallinity and very few interfacial defects. Between 800 and 900 sccm of 10% C2H4 in He, the C content increased dramatically from 2% to 10% and the as-grown films changed from crystalline to amorphous. In order to establish deposition conditions for the crystalline-amorphous phase transformation, one SiGeC film was deposited as the 10% C2H4 flow was increased linearly from 500 to 1500 sccm during growth. When the C content reached ∼4%, the film developed considerable stacking defects and disorder, and at around 11% C, the film became amorphous.

Epitaxial Si/praseodymium oxide/Si heterostructures were grown in situ on (111) oriented Si substrates using pulsed laser deposition. Growth of the oxide layer under oxygen deficient conditions resulted in hexagonal Pr2O3 (h-Pr2O3) films which displayed a (001)Pr2O3∥(111)Si, [110]Pr2O3∥[11̄0]Si orientation and x-ray rocking curve full width at half-maximum values of ∼0.8°. The top Si layer grew epitaxially on the oxide film with a twinned (111)Si∥(001)Pr2O3 orientation. The surface structure of both oxide and semiconductor layers was investigated in situ using reflection high energy electron diffraction, and the resulting films were characterized using x-ray diffraction and transmission electron microscopy.

For very thin Co layers, the exchange coupling between adjacent Co layers in Co/ Pt multilayers is ferromagnetic and the coupling strength varies nonmonotonically as the nonmagnetic Pt layer thickness ͑t Pt ͒ ranges from 3 to 75 Å. We report on the magnetization reversal process in a series of ͓Co͑4 Å͒ /Pt͑t Pt ͔͒ N multilayers observed by magneto-optical Kerr microscopy as a function of t Pt and layer repetition N. The images reveal the evolution of magnetic reversal processes that strongly depend on t Pt and therefore on the interlayer coupling. For Co/ Pt multilayers with small t Pt , e.g., 11 Å, where the Co layers are strongly coupled, the whole multilayer switches as a single ferromagnet. As Co layers are separated farther and become weakly coupled, e.g., at t Pt = 41 Å, layer-by-layer magnetic reversal is observed. The Kerr images reveal metastable magnetic domain configurations during layer-by-layer switching which is not evident in the measured hysteresis loops during the abrupt magnetic reversal for Co/ Pt multilayers with weak interlayer coupling at large t Pt .

Pseudomorphic SiGeC films have been grown on (100) Si by atmospheric pressure chemical vapor deposition at 600 and 700 °C using SiH2Cl2, GeH4, and C2H4 precursors. Films with C concentrations of up to 2.5 at. % were entirely pseudomorphic and a 120-nm-thick Si66.5Ge31C2.5 film had 90% substitutional carbon. With increasing C incorporation due to increased ethylene flow, a layered structure was formed consisting of an amorphous film overlaying a buried pseudomorphic film. The crystalline-to-amorphous transition was initiated by the accumulation of C on the epitaxial growth surface. This deteriorated surface resulted in the formation of stacking faults along {111} planes and subsequent amorphization. Defect formation and amorphization could be prevented by periodically growing a thin Si epilayer.