Holger Baur

Triple stack glass-to-glass anodic bonding for optogalvanic spectroscopy cells with electrical feedthroughs

We demonstrate the use of an anodic bonding technique for building a vacuum tight vapor cell for the use of Rydberg spectroscopy of alkali atoms with thin film electrodes on the inside of the cell. The cell is fabricated by simultaneous triple stack glass-to-glass anodic bonding at 300 °C. This glue-free, low temperature sealing technique provides the opportunity to include thin film electric feedthroughs. The pressure broadening is only limited by the vapor pressure of rubidium and the lifetime is at least four months with operating temperatures up to 230 °C.

Nonequilibrium transfer and decoherence in quantum impurity problems

Using detailed balance and scaling properties of integrals that appear in the Coulomb gas reformulation of quantum impurity problems, we establish exact relations between the nonequilibrium transfer rates of the boundary sine-Gordon and the anisotropic Kondo model at zero temperature. Combining these results with findings from the thermodynamic Bethe ansatz, we derive exact closed form expressions for the transfer rate in the biased spin-boson model in the scaling limit. They illustrate how the crossover from weak to strong tunneling takes place. Using a conjectured correspondence between the transfer and the decoherence rate, we also determine the exact lower bound for damping of the coherent oscillation as a function of bias and dissipation strength in this paradigmic model for NMR and superposition of macroscopically distinct states (qubits).

62.2: AMLCD with Carbon‐Nanotube Pixel Electrodes

We have realized a full color 4-inch quarter-VGA amorphous-Silicon AMLCD with pixel electrodes made of random carbon nanotube (CNT) networks instead of ITO. The CNTs are deposited from suspension by spray-coating. with this work we demonstrate the applicability of CNT pixel electrodes in a standard AMLCD process.

Low temperature processes for metal-oxide thin film transistors

Processes for realizing ohmic drain/source contacts and a multilayer dielectric for sputtered amorphous oxide thin film transistors with high throughput at 160°C combined with a back-channel etch process have been demonstrated. These transistors achieve a carrier mobility of 8.6 cm2/Vs, a subthreshold slope of 0.18 V/dec, threshold voltage of 2.54 V and on/off ratio above 107. The chosen backchannel etch approach can also be extended to be used with drain/source metals such as molybdenum or copper.

Active‐matrix OLED backplanes based on LTPS for small molecules and polymers

— A four-mask low-temperature poly-Si (LTPS) TFT process for p- and n-channel devices has been developed. PECVD-deposited amorphous silicon was recrystallized to polycrystalline-silicon with single-area excimer-laser crystallization, while the gate dielectric was fabricated by PECVD deposition of a SiH4-N2O-based silicon oxide. Formation of drain and source was carried out with self-aligned ion-beam implantation. To prove the potential capability of these devices, which are suitable for conventional and inverted OLEDs alike, several functional active-matrix backplanes implementing different pixel circuits have been produced. This active-matrix backplane process has been customized to drive small molecules as well as polymers regardless if its structure is top or bottom emitting.

An LTPS active-matrix process with PECVD doped N+ drain/source areas

— A low-temperature polysilicon active-matrix process without the need for ion implantation to dope drain and source areas of TFTs has been developed. A doped silicon layer is deposited by PECVD and structured prior to the deposition of the intrinsic silicon for the channel. The dopant is diffused and activated during the excimer-laser crystallization step. N-channel test TFTs with different geometries were realized. The TFT properties (mobility, on/off ratio, saturation, etc.) are suitable to realize AMLCDs and AMOLED displays and to integrate driver electronics on the displays. In addition to simple TFTs, a full-color 4-in. quarter-VGA AMLCD was realized. The complete display (including photolithographic masks, active-matrix backplane, and color-filter/black-matrix frontplane), and an addressing system were developed and manufactured at the Chair of Display Technology, University of Stuttgart, Germany. The substitution of ion doping by PECVD deposition overcomes a major limitation for panel sizes in poly-Si technology and avoids large investment costs for ion-implantation equipment.

33.4: Distinguished Student Paper: An LTPS Active‐Matrix Process without Ion Doping

A low temperature poly-silicon active matrix process without the need for ion implantation to dope drain and source areas of TFTs has been developed. A doped silicon layer is deposited by PECVD and structured prior to the deposition of the intrinsic silicon for the channel. The dopant is diffused and activated within the excimer laser crystallization step. N-channel test TFTs with different geometries and a 4 inch quarter-VGA AMLCD were realized. The TFT properties (mobility, on/off ratio, saturation, etc.) are suitable to realize AMLCDs, AMOLED displays and to integrate driver electronics on the displays. The substitution of ion doping by PECVD deposition overcomes a major limitation for panel sizes in poly-Si technology and avoids large investment costs for ion implantation equipment.

A transimpedance amplifier based on an LTPS process operated in alkali vapor for the measurement of an ionization current

Rydberg atoms in room temperature vapor cells are promising candidates for realizing new kinds of quantum devices and sensors. However, the alkali vapor, which is most commonly used, introduces new technological challenges. We demonstrate the applicability of anodic bonding as a sealing method for vapor cells, which preserves vacuum levels down to 10-7 mbar for several years, while being compatible with thin-film electronics on glass. We furthermore prove, that the implementation of such thin-film electronics inside a highly reactive atmosphere of alkali vapor is possible. We also propose a new kind of gas sensor based on Rydberg excitations as a competitive and promising application of our Rydberg detection scheme.

Proof of concept for an optogalvanic gas sensor for NO based on Rydberg excitations

We demonstrate the applicability of 2-photon Rydberg excitations of nitric oxide (NO) at room temperature in a gas mixture with helium (He) as an optogalvanic gas sensor. The charges created initially from succeeding collisions of excited NO Rydberg molecules with free electrons are measured as a current on metallic electrodes inside a glass cell and amplified using a custom-designed highbandwidth transimpedance amplifier attached to the cell. We fnd that this gas sensing method is capable of detecting NO concentrations lower than 10 ppm even at atmospheric pressures, currently only limited by the way we prepare the gas dilutions.

7.1: Invited Paper: LTPS Processes for AMLCD and AMOLED Applications

Cost efficient PMOS, NMOS and CMOS LTPS processes have been developed. The practical viability of these processes was demonstrated by building logic circuits as well as entire AMLCD and AMOLED display systems including integration of the various display effects, module fabrication and driver electronics design.