Yttrium and Scandium in Solution-processed Oxide Electronic Materials.

Large area electronics are critical for many novel applications such as smart windows, wearable electronics and Internet of Things. Among candidate materials, metal oxides have relatively good performance and stability and can be deposited by low-cost solution processes. This thesis explores the roles of rare-earth elements yttrium and scandium in solution-processed metal oxide thin films including semiconducting scandium- or yttrium-doped ZTO, conducting scandium- or yttrium-doped zinc oxide, and insulating yttrium-scandium oxide. Yttrium and scandium can act as oxygen getters and stabilizers, and the use of higher-order alloys can improve film thermal stability and electrical performance. First, thin film transistors (TFTs) are used to characterize undoped ZTO films as a baseline. The device performance of solution-processed ZTO TFTs depends on ink Zn to Sn ratio and annealing temperature, optimized to be 7:3 and 480⁰C, respectively. The optimized ZTO has a shallow donor energy level of 7meV and a steep exponential subgap band tail with a percolation energy of 3meV. Sputtered Mo forms an excellent ohmic contact to solution-processed ZTO with a width-normalized contact resistance of 8.7Ω•cm and a transfer length of 0.34μm, making the technology suitable for future sub-micron channel length devices. Yttrium enhances performance of ZTO TFTs at low concentrations (3at%). High yttrium concentrations slightly improve TFT negative bias illumination stress stability by reducing oxygen vacancy-related defects. Second, the introduction of scandium or yttrium in solution-processed ZnO decreases the conductivity by three orders of magnitude, which is ascribed to formation of insulating structures along grain boundaries. Scandium or yttrium also make the resistivity of ZnO more thickness-dependent than undoped ZnO after forming gas anneal, by causing surface depletion and grain disruptions in the film. Third, solution-processed (YxSc1-x)2O3 insulating alloys have comparable dielectric performance to vacuum deposited (YxSc1-x)2O3, with high breakdown field > 4MV/cm, low leakage current and low dielectric frequency dispersion. Even after 900°C anneals induce crystallization, the alloys maintain a high breakdown field. The yttrium- and scandium- doped solution-processed oxides developed here form a complete suite of electronic materials suitable for fabrication of future large-area electronic devices.PhDElectrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/133324/1/wbhu_1.pd

Free-energy barrier to melting of single-chain polymer crystallite

We report Monte Carlo simulations of the melting of a single-polymer crystallite. We find that, unlike most atomic and molecular crystals, such crystallites can be heated appreciably above their melting temperature before they transform to the disordered "coil" state. The surface of the superheated crystallite is found to be disordered. The thickness of the disordered layer increases with superheating. However, the order-disorder transition is not gradual but sudden. Free-energy calculations reveal the presence of a large free-energy barrier to melting.Comment: AMS-Latex, 4 pages with 5 figures, submitted to Phys. Rev. Let

Lattice model study of the thermodynamic interplay of polymer crystallization and liquid-liquid demixing

We report Monte Carlo simulations of a lattice-polymer model that can account for both polymer crystallization and liquid-liquid demixing in solutions of semiflexible homopolymers. In our model, neighboring polymer segments can have isotropic interactions that affect demixing, and anisotropic interactions that are responsible for freezing. However, our simulations show that the isotropic interactions also have a noticeable effect on the freezing curve, as do the anisotropic interactions on demixing. As the relative strength of the isotropic interactions is reduced, the liquid-liquid demixing transition disappears below the freezing curve. A simple, extended Flory-Huggins theory accounts quite well for the phase behavior observed in the simulations.Comment: Revtex, 7 pages, the content accepted by J. Chem. Phy

Correlation of expressions of S100A8 and S100A9 and its prognostic potential in nasopharyngeal carcinoma

Purpose: To investigate the expressions of S100 calcium-binding proteins A8 (S100A8) and S100 A9 (S100A9) in nasopharyngeal carcinoma (NPC) tissues and their correlation with clinical pathological characteristics and prognosis of NPC.Methods: Ninety-two NPC tissue samples and 92 nasopharyngitis tissue samples (controls) were collected. All the NPC patients were on follow-up for more than 5 years. The expressions of S100A8 and S100A9 were determined in these tissues by immunohistochemistry. The relationship between the expressions of S100A8 and S100A9, and the clinico-pathological features were analyzed by Spearman correlation analysis, and the results evaluated by Kaplan-Meier method.Results: The differences between their expressions in the two tissues were statistically significant (p < 0.05). Neither gender nor age was associated with expressions of S100A8 and S100A9 (p > 0.05), but they were closely related to the degree of differentiation, clinical stages and metastasis of lymph node (p < 0.05). The expression of S100A8 had significant positive correlation with the expression of S100A9 (r = 0.393, p = 0.000). Prognosis of patients with positive expressions of S100A8 and S100A9 was poor, when compared to patients with negative expressions of these proteins (p < 0.05).Conclusion: Expressions of S100A8 and S100A9 are closely related to the development of NPC. High expressions of the two proteins may have an important influence in the progress of tumor invasion but are associated with poor prognosis of NPC. These findings could be significant indicators of early diagnosis, effectiveness of treatment and prognosis of NPC.Keywords: S100A8, S100A9, Calcium-binding proteins, Prognosis, Nasopharyngeal carcinoma, Prognosi

Radiomics Signature on Computed Tomography Imaging: Association With Lymph Node Metastasis in Patients With Gastric Cancer

Background: To evaluate whether radiomic feature-based computed tomography (CT) imaging signatures allow prediction of lymph node (LN) metastasis in gastric cancer (GC) and to develop a preoperative nomogram for predicting LN status.Methods: We retrospectively analyzed radiomics features of CT images in 1,689 consecutive patients from three cancer centers. The prediction model was developed in the training cohort and validated in internal and external validation cohorts. Lasso regression model was utilized to select features and build radiomics signature. Multivariable logistic regression analysis was utilized to develop the model. We integrated the radiomics signature, clinical T and N stage, and other independent clinicopathologic variables, and this was presented as a radiomics nomogram. The performance of the nomogram was assessed with calibration, discrimination, and clinical usefulness.Results: The radiomics signature was significantly associated with pathological LN stage in training and validation cohorts. Multivariable logistic analysis found the radiomics signature was an independent predictor of LN metastasis. The nomogram showed good discrimination and calibration.Conclusions: The newly developed radiomic signature was a powerful predictor of LN metastasis and the radiomics nomogram could facilitate the preoperative individualized prediction of LN status