Semiconductor In 1874, Braun discovered the asymmetric conduction properties of certain materials, which became the foundation for the point-contact
rectifier. This discovery showed that certain
metal-semiconductor junctions could conduct electricity more easily in one direction than the other, a crucial property for
diodes. Braun's work with semiconductors led to the development of the first
point-contact diode, often credited as a basic semiconductor device that allowed the rectification of
alternating current into
direct current. This is important because it was one of the first real-world applications of semiconducting materials, paving the way for future
semiconductor devices that would later evolve into modern diodes,
transistors, and other semiconductor technology. Braun's discoveries were instrumental in the early development of
electronics and helped lay the groundwork for the
semiconductor industry we know today.
Cathode-ray tube Braun's enduring fame is largely due to his invention of the
cathode-ray tube (CRT), which is still commonly referred to as the "Braun tube"; today, the term typically refers to a high-vacuum tube, in which an electron beam can be deflected in both horizontal and vertical directions. The first version, developed in Strassburg in 1897, was far from perfect; it featured a
cold cathode and a moderate vacuum, which required a 100,000 V
acceleration voltage to produce a visible trace of the magnetically deflected beam. Furthermore, magnetic deflection affected only one direction, while the other was controlled by a rotating mirror placed in front of the
phosphorescent screen. However, industry immediately recognized the potential of the invention, leading to its further development. By 1899, his assistant,
Jonathan Zenneck, introduced oscillations to magnetically control the Y deflection, and later improvements included the addition of a heated cathode, a
Wehnelt cylinder, and high-vacuum technology. This tube was not only used for
oscilloscopes, but also for fully
electronic television transmission as a picture tube for
television sets, although Braun had considered it unsuitable for television. The CRT became the cornerstone in developing fully electronic television, being a part of every TV, computer, and any other screen setup till the introduction of the
LCD screen at the end of the 20th century. It is still occasionally called the "Braun tube" in German-speaking countries () and other countries such as Korea (브라운관:
Buraun-kwan) and Japan (:
Buraun-kan).
Radio receiver invented by Braun used in the coherer radio receivers in wireless telegraphy radio systems made by the
Telefunken company in 1903 Following the invention of his tube, Braun began researching in the field of
wireless telegraphy. A key issue in early radio technology was the development of a reliable receiver. Braun, as a physicist, was accustomed to working under reproducible experimental conditions, which the commonly used
coherer receivers at the time failed to meet. He replaced the coherer with a
crystal detector, which greatly improved the sensitivity of the receiver, although the crystal detector required frequent re-adjustment. It was only later that the
electron tube replaced the crystal detector, although devices like germanium diodes continued to be used in simpler receivers for some time. The first FM
radar systems still employed a crystal detector. In late 1898, the technology was commercialized when the chocolate manufacturer from Cologne, Ludwig Stollwerck, founded a consortium to exploit Braun's patents, contributing 560,000 marks in capital. After the successful transmission of signals over longer distances, the consortium was transformed into the "Professor Braun’s Telegraphy Company," which eventually became
Telefunken AG. They set up the first world-wide network of communications, and was the first in the world to sell electronic televisions with
cathode-ray tubes in Germany in 1934. In 1900, Stollwerck facilitated contact with Professor August Raps, head of the
Siemens & Halske Telegraph Construction Company, which later took over the development of the apparatus. See more:
Crystal detector Radio transmitter Braun also made significant contributions to radio transmission technology. While
Guglielmo Marconi had developed his transmitter primarily through empirical methods, Braun was able to improve it by focusing on the underlying physics. Originally, the resonant and antenna circuits were combined, but he separated them into two parts: a primary circuit consisting of a
capacitor and spark gap, and an antenna circuit inductively coupled to it. This innovation allowed for greater energy transmission in the system. By 1898, the resulting powerful systems made the term "long-distance telegraphy" more appropriate, as the maximum range, previously limited to 20 km, steadily increased. On 24 September 1900, a radio link was successfully established between
Cuxhaven and
Helgoland over a distance of 62 km. On 12 December 1901, Marconi received radio signals at his station in
Poldhu, Cornwall, at Signal Hill in
St. Johns, Newfoundland, using a transmitter designed in Braun's circuit. Whether this reception actually occurred remains debated in the literature. Meanwhile, Braun attempted to replace the spark-gap transmitter, which produced damped oscillations, with AC generators that generated undamped oscillations, though he was unable to implement a feedback loop using electron tubes at the time. Together with
Georg Graf von Arco and
Adolf Slaby, Braun was part of the team that developed the concept for "mobile stations for wireless telegraphy for military purposes," which in 1903 led to a practical implementation by
AEG and Siemens & Halske. The system consisted of two horse-drawn wagons: one with all the transmitting and receiving equipment, including a battery, and the other with auxiliary and reserve supplies. This allowed the wagons to be separated in difficult terrain, as the station could still operate with just the front wagon. See more:
Wireless telegraphy Antennas Braun also focused on early problems in directional radio—the alignment of transmitting and receiving antennas. He was among the first to achieve directed radiation and optimized antenna performance through calculations.
Electroscope Braun is also credited with the invention of the pointer
electroscope, which was named after him. == Awards ==