Engineering thin films of magnetic alloys and semiconductor oxides at the nanoscale

The thesis aims to exploit properties of thin films for applications such as spintronics, UV detection and gas sensing. Nanoscale thin films devices have myriad advantages and compatibility with Si-based integrated circuits processes. Two distinct classes of material systems are investigated, namely ferromagnetic thin films and semiconductor oxides. To aid the designing of devices, the surface properties of the thin films were investigated by using electron and photon characterization techniques including Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), grazing incidence X-ray diffraction (GIXRD), and energy-dispersive X-ray spectroscopy (EDS). These are complemented by nanometer resolved local proximal probes such as atomic force microscopy (AFM), magnetic force microscopy (MFM), electric force microscopy (EFM), and scanning tunneling microscopy to elucidate the interplay between stoichiometry, morphology, chemical states, crystallization, magnetism, optical transparency, and electronic properties. Specifically, I studied the effect of annealing on the surface stoichiometry of the CoFeB/Cu system by in-situ AES and discovered that magnetic nanoparticles with controllable areal density can be produced. This is a good alternative for producing nanoparticles using a maskless process. Additionally, I studied the behavior of magnetic domain walls of the low coercivity alloy CoFeB patterned nanowires. MFM measurement with the in-plane magnetic field showed that, compared to their permalloy counterparts, CoFeB nanowires require a much smaller magnetization switching field , making them promising for low-power-consumption domain wall motion based devices. With oxides, I studied CuO nanoparticles on SnO2 based UV photodetectors (PDs), and discovered that they promote the responsivity by facilitating charge transfer with the formed nanoheterojunctions. I also demonstrated UV PDs with spectrally tunable photoresponse with the bandgap engineered ZnMgO. The bandgap of the alloyed ZnMgO thin films was tailored by varying the Mg contents and AES was demonstrated as a surface scientific approach to assess the alloying of ZnMgO. With gas sensors, I discovered the rf-sputtered anatase-TiO2 thin films for a selective and sensitive NO2 detection at room temperature, under UV illumination. The implementation of UV enhances the responsivity, response and recovery rate of the TiO2 sensor towards NO2 significantly. Evident from the high resolution XPS and AFM studies, the surface contamination and morphology of the thin films degrade the gas sensing response. I also demonstrated that surface additive metal nanoparticles on thin films can improve the response and the selectivity of oxide based sensors. I employed nanometer-scale scanning probe microscopy to study a novel gas senor scheme consisting of gallium nitride (GaN) nanowires with functionalizing oxides layer. The results suggested that AFM together with EFM is capable of discriminating low-conductive materials at the nanoscale, providing a nondestructive method to quantitatively relate sensing response to the surface morphology.

Screening Diversity: Women & Work in Twenty-First-Century Popular Culture

Screening Diversity: Women and Work in Twenty-first Century Popular Culture explores contemporary representations of diverse professional women on screen. Audiences are offered successful women with limited concerns for feminism, anti-racism, or economic justice. I introduce the term viewsers to describe a group of movie and television viewers in the context of the online review platform Internet Movie Database (IMDb) and the social media platforms Twitter and Facebook. Screening Diversity follows their engagement in a representative sample of professional women on film and television produced between 2007 and 2015. The sample includes the television shows, Scandal, Homeland, VEEP, Parks and Recreation, and The Good Wife, as well as the movies, Zero Dark Thirty, The Proposal, The Heat, The Other Woman, I Don’t Know How She Does It, and Temptation. Viewsers appreciated female characters like Olivia (Scandal), and Maya (Zero Dark Thiry) who treated their work as a quasi-religious moral imperative. Producers and viewsers shared the belief that unlimited time commitment and personal identification were vital components of professionalism. However, powerful women, like The Proposal’s Margaret and VEEP’s Selina, were often called bitches. Some viewsers embraced bitch-positive politics in recognition of the struggles of women in power. Women’s disproportionate responsibility for reproductive labor, often compromises their ability to live up to moral standards of work. Unlike producers, viewsers celebrated and valued that labor. However, texts that included serious consideration of women as workers were frequently labelled chick flicks or soap operas. The label suggested that women’s labor issues were not important enough that they could be a topic of quality television or prestigious film, which bolstered the idea that workplace equality for women is not a problem in which the general public is implicated. Emerging discussions of racial injustice on television offered hope that these formations are beginning to shift.