Matching Items (447)
Description
Semiconductor nanowires are featured by their unique one-dimensional structure which makes them promising for small scale electronic and photonic device applications. Among them, III-V material nanowires are particularly outstanding due to their good electronic properties. In bulk, these materials reveal electron mobility much higher than conventional silicon based devices, for example at room temperature, InAs field effect transistor (FET) has electron mobility of 40,000 cm2/Vs more than 10 times of Si FET. This makes such materials promising for high speed nanowire FETs. With small bandgap, such as 0.354 eV for InAs and 1.52 eV for GaAs, it does not need high voltage to turn on such devices which leads to low power consumption devices. Another feature of direct bandgap allows their applications of optoelectronic devices such as avalanche photodiodes. However, there are challenges to face up. Due to their large surface to volume ratio, nanowire devices typically are strongly affected by the surface states. Although nanowires can be grown into single crystal structure, people observe crystal defects along the wires which can significantly affect the performance of devices. In this work, FETs made of two types of III-V nanowire, GaAs and InAs, are demonstrated. These nanowires are grown by catalyst-free MOCVD growth method. Vertically nanowires are transferred onto patterned substrates for coordinate calibration. Then electrodes are defined by e-beam lithography followed by deposition of contact metals. Prior to metal deposition, however, the substrates are dipped in ammonium hydroxide solution to remove native oxide layer formed on nanowire surface. Current vs. source-drain voltage with different gate bias are measured at room temperature. GaAs nanowire FETs show photo response while InAs nanowire FETs do not show that. Surface passivation is performed on GaAs FETs by using ammonium surfide solution. The best results on current increase is observed with around 20-30 minutes chemical treatment time. Gate response measurements are performed at room temperature, from which field effect mobility as high as 1490 cm2/Vs is extracted for InAs FETs. One major contributor for this is stacking faults defect existing along nanowires. For InAs FETs, thermal excitations observed from temperature dependent results which leads us to investigate potential barriers.
ContributorsLiang, Hanshuang (Author) / Yu, Hongbin (Thesis advisor) / Ferry, David (Committee member) / Tracy, Clarence (Committee member) / Arizona State University (Publisher)
Created2011
Description
Black Laurel is a book-length manuscript which has at its center poems that reveal and explore issues related to Michele Poulos's identity as a Greek-American writer, discovering the connections that link the past and present of both Greece and America. These poems often work as a quest to recover identity. They explore the idea that it is her own privileged perspective as an educated Greek-American woman that both allows and in some ways prevents her seeing herself in the Greeks who today are struggling economically, emotionally, and psychologically. Many of the poems work to achieve a complex understanding of both an individual as well as a broader cultural history. These poems sometimes take on the personas of striking figures from other times and other landscapes, while others draw on materials which are somewhat more autobiographical. In one poem titled "Before My Mother Set Herself on Fire," the speaker is an imagined daughter in a modern-day Greek family. The poem, inspired by a news story about an elderly man who shot himself in the head in front of Syntagma Square in Athens to protest the austerity measures imposed on the Greek population, explores the various ways in which a national crisis may affect an individual family. Alternatively, Poulos delves into her personal family history in "When the Wind Falls," a poem about the Nazi invasions of northern Greece. At the same time, this focus on past and present Greece is only one strand in a wide-ranging manuscript woven of materials which also include a variety of subjects related to science, history, eroticism, mysticism, and much more.
ContributorsPoulos, Michele (Author) / Dubie, Norman (Thesis advisor) / Hogue, Cynthia (Committee member) / Hummer, Terry (Committee member) / Arizona State University (Publisher)
Created2013
Description
Chris Miller's Souvenirs of Sleep is as serious as it is whimsical, if this is a possibility. The "Museum of the Zoo-real" may be an equally appropriate title as animals are often in performance. In this visual and spiritual investigation, childhood, dream, and the loss of a mother to suicide are the currents. Miller's work is informed by the cinema of Werner Herzog, Andrei Tarkovsky, Robert Bresson and beyond. Miller believes in the power of implication. The poems begin with intense focus, but are often in the business of expansion. Souvenirs of Sleep is a journey toward sense-making, a search for language that might allow it.
ContributorsMiller, Christopher (Author) / Dubie, Norman (Thesis advisor) / Hogue, Cynthia (Committee member) / Ball, Sally (Committee member) / Arizona State University (Publisher)
Created2013
Description
Cruz del Sur is an exploration of what it means to be an outsider: as a resident, as a foreigner, from the perspective of the human eye, or from the perspective of a camera lens. An unlikely blending of voices, these poems embark the reader on a journey across a continent, and also into an interior: a mystical quest.
ContributorsMontgomery, Scott (Author) / Dubie, Norman (Thesis advisor) / Hogue, Cynthia (Committee member) / Hummer, Terry (Committee member) / Arizona State University (Publisher)
Created2013
Description
The Fledglings of Anani is a universe with an underlying organizing principle of desire, auspiciousness and serendipity, the veiled doors and windows of these realms serve as fugues bridging layers of time leading us through myth and landscape intimately tied to the physical intelligence of earth and character of place. It is a voice that comes to know itself first as being, then in correspondence to nature and her elements, enters into the rhythm of human connection and ultimately circles back to comprehend itself as all these things, varying only in degree. The poems travel further and further toward an allusive center with a contemplative inner eye that embraces the complexity and vitality of life.
ContributorsPoole, Heather Lea (Author) / Dubie, Norman (Thesis advisor) / Hogue, Cynthia (Committee member) / Savard, Jeannine (Committee member) / Arizona State University (Publisher)
Created2012
Description
A collection of poems that explore what it means to be from the Atomic City-- a city built atop cleared-out rural communities in East Tennessee during World War II, and with the sole and secretive purpose of enriching uranium for the atomic bomb. The poems look back to the more isolated Appalachian culture of previous generations, discovering the identity rifts caused by such massive and rushed development. In trying to understand the poet's own cultural inheritance of both nuclear weaponry and an Appalachian hardness, the poems begin to meditate on inhabitation. They ask what it means to live in a country, a local community, a body. The poems travel far beyond the Atomic City's limits, incorporating characters that live, in some sense, at the edge of a community. As he crosses the Atlantic, the Spanish poet Jiménez wonders if either sound or vision are more trustworthy tools for perception; an aging grandmother in Tennessee realizes that she still "drives" her younger body in her dreams; an American woman becomes aroused after touring the killing fields in Cambodia; and the prophet of Oak Ridge, who supposedly predicted the Manhattan Project, considers how his baby daughter has become a thing after death. The various voices show the poet grappling with her own guilt over Hiroshima, and ultimately attempt to understand the limits of both grief and love, how one inherits a tragedy.
ContributorsSams, Sara (Author) / Hogue, Cynthia (Thesis advisor) / Ball, Sally (Committee member) / Dubie, Norman (Committee member) / Arizona State University (Publisher)
Created2013
Description
This creative thesis is a work of narrative and lyric poetry. Death and Nature are two complex themes that emerge frequently in the poems and work as well across the breadth of the manuscript. The speakers' perspectives vary and are indebted to two sub-genres of poetry, namely--The Poetry of Witness, and Ekphrastic Poetry. Their psycho-analytic underpinnings are at times indisputable, and at other times, purely subjective. Many poems address political and human rights issues in the Middle East, and in the rest of the world. It is here that the poems depend and reveal flexibility with diction and varying structures. Overall, the poems reflect and investigate possible restraints and choices, both internally by the details and images, and externally by multiple experiments with free verse forms.
ContributorsHassan, Eman (Author) / Dubie, Norman (Thesis advisor) / Hogue, Cynthia (Committee member) / Savard, Jeannine (Committee member) / Arizona State University (Publisher)
Created2012
Description
The poems in this book are lyric, meditational, and narrative approaches to autobiographical tales. These works, through various poetic forms, are an attempt to assess and equate personal life experiences with those larger human and universal occasions. Spanning both physical time (a cross-country move from Virginia to Arizona) and spatial time (Virginia and Mississippi during the civil rights movement), the works evaluate and validate the human experiences of loss. Through poems addressed to various family members and historical figures, the book attempts to terms with the often humorous, often terrifying experience of being an African American male in the United States in the 21st Century.
ContributorsBooth, Dexter (Author) / Dubie, Norman (Thesis advisor) / Hummer, Terry (Committee member) / Fritz-Goldberg, Beckian (Committee member) / Arizona State University (Publisher)
Created2012
Description
ABSTRACT An Ensemble Monte Carlo (EMC) computer code has been developed to simulate, semi-classically, spin-dependent electron transport in quasi two-dimensional (2D) III-V semiconductors. The code accounts for both three-dimensional (3D) and quasi-2D transport, utilizing either 3D or 2D scattering mechanisms, as appropriate. Phonon, alloy, interface roughness, and impurity scattering mechanisms are included, accounting for the Pauli Exclusion Principle via a rejection algorithm. The 2D carrier states are calculated via a self-consistent 1D Schrödinger-3D-Poisson solution in which the charge distribution of the 2D carriers in the quantization direction is taken as the spatial distribution of the squared envelope functions within the Hartree approximation. The wavefunctions, subband energies, and 2D scattering rates are updated periodically by solving a series of 1D Schrödinger wave equations (SWE) over the real-space domain of the device at fixed time intervals. The electrostatic potential is updated by periodically solving the 3D Poisson equation. Spin-polarized transport is modeled via a spin density-matrix formalism that accounts for D'yakanov-Perel (DP) scattering. Also, the code allows for the easy inclusion of additional scattering mechanisms and structural modifications to devices. As an application of the simulator, the current voltage characteristics of an InGaAs/InAlAs HEMT are simulated, corresponding to nanoscale III-V HEMTs currently being fabricated by Intel Corporation. The comparative effects of various scattering parameters, material properties and structural attributes are investigated and compared with experiments where reasonable agreement is obtained. The spatial evolution of spin-polarized carriers in prototypical Spin Field Effect Transistor (SpinFET) devices is then simulated. Studies of the spin coherence times in quasi-2D structures is first investigated and compared to experimental results. It is found that the simulated spin coherence times for GaAs structures are in reasonable agreement with experiment. The SpinFET structure studied is a scaled-down version of the InGaAs/InAlAs HEMT discussed in this work, in which spin-polarized carriers are injected at the source, and the coherence length is studied as a function of gate voltage via the Rashba effect.
ContributorsTierney, Brian David (Author) / Goodnick, Stephen (Thesis advisor) / Ferry, David (Committee member) / Akis, Richard (Committee member) / Saraniti, Marco (Committee member) / Vasileska, Dragica (Committee member) / Arizona State University (Publisher)
Created2011
Description
Dark Tourism explores the grief borne of losing a connection to the past. As detailed in the prologue poem, "Baucis and Philemon," the speaker's stories in Dark Tourism "have been resistant / to [their] drownings" and that refusal to stay buried has "[sent] ripples in every direction." The voices in Dark Tourism track the trajectory of these ripples by animating the past, especially through the formal work in the partial sonnet crown that acts as centerpiece to the manuscript. The sonic and rhythmic repetitions reinforce an idea central to Dark Tourism as a whole: the things we inherit from the past endure, with or without our permissions, and the speakers seek to interpret this haunting in a way that unifies past and present.
ContributorsAndoga, Rachel (Author) / Savard, Jeannine (Thesis advisor) / Dubie, Norman (Committee member) / Hogue, Cynthia (Committee member) / Arizona State University (Publisher)
Created2012