M. Dipalo

Thermally Actuated Nanocrystalline Diamond Micro-Bridges for Microwave and High Power RF Applications

This paper presents a thermally actuated nanocrystalline diamond micro-bridge for RF and high power applications. The diamond bridges are integrated on a CPW transmission line and small signal measurements of the actuator working as a switch are presented. The bridges are actuated at 2 volts drawing a current of 30 mA. Tunable inductors with an inductance ratio of 2.2 at 30 GHz are also presented. High power measurements in the range of 24-47 dBm for the diamond actuator in a microstrip topology are presented.

High power nanocrystalline diamond RF MEMS- A combined look at mechanical and microwave properties

In this paper, a compressively stressed nanocrystalline diamond (NCD) actuator utilizing a thermal actuation scheme is presented. The growth chemistry of NCD films along with the mechanical properties of diamond are discussed in detail. Stress engineering is performed to realize compressively stressed diamond films for RF-MEMS applications. A NCD based bi-stable actuator is designed and fabricated on a low resistive silicon substrate. Tunable switches are implemented in CPW and microstrip topologies and small signal measurements are performed in the frequency range of 5-30 GHz. High power measurements are performed in the power spectrum of 24-47 dBm on the switches integrated in the microstrip topology.

Thick nano-crystalline diamond overgrowth on InAlN/GaN devices for thermal management

The use of high quality diamond overlayers as heat sink has been studie d extensively in the past two decade s for high power devices. The outstanding diamond thermal conductivity would indeed enable to extract the extremely high power density of GaN-based devices, whose operation is often limited to pulse mode to prevent excessive device overheating [1].

XPS Study of In Situ One-Step Amination of Nanocrystalline Diamond Films

In the present work two different in situ amination of hydrogenated nano-crystalline diamond surfaces were studied. The effects of an UV irradiation in pure ammonia gas were compared to those produced in a mixture of pure ammonia gas with a small amount of pure oxygen. In situ XPS analysis was used to study the evolution of surface terminations from “C-H” to “CNH2”. As we will show in this work, the grafting of NH2 functional groups to the diamond surface is mediated by oxygen indicating that oxygen plays a crucial role in the process of amination.

A Concept for Diamond Overlayers on Nitride Heterostructures

The development of diamond overlayers with high crystalline quality for high power devices in Si, GaAs or GaN, aimed at heat extraction from the top, has been a quest for many years. Recently CMOS circuits have been coated by untra-nano-crystalline-diamond (UNCD) grown at 350 C, however with low thermal conductivity due to a substantial graphitic grain boundary content [1]. Usual growth conditions for nanocrystalline diamond (NCD) films of high thermal conductivity are a temperature above 600 C in hydrogen atmosphere with high H* radical concentration and CH4 growth chemistry. In fact, no such overlayer with high thermal conductivity has been developed to our knowledge up to now for GaAs or GaN. However, GaN based power devices are already presently seriously limited by their thermal losses and even the employment of diamond substrate heat spreaders may not be sufficient. Such substrate heat spreader configurations are usually realized by joining prefabricated semiconductor and diamond materials stacks by alloying or wafer bonding.